[22] DIRECT FORMATION OF HOT ELECTRON INJECTING NANOSTRUCTURES FOR PHOTOVOLTAICS
Hannah Noa Barad1, Adam Ginsburg2, Kevin Rietwyk2, Hagai Cohen3, David A Keller4, Shay Tirosh2, Assaf Anderson2, Arie Zaban2
1 Bar Ilan University; Department of Chemistry
2 Bar Ilan University; Bar Ilan University
3 Weizmann Institute of Science; Weizmann Institute of Science
4 Bar-Ilan University; Bar-Ilan University
Direct Formation of Hot Electron Injecting Nanostructures for Photovoltaics
Hannah-Noa Barada, Adam Ginsburga, Kevin J. Rietwyka, Hagai Cohenb, David A. Kellera, Shay Tirosha, Assaf Y. Anderson*,a, and Arie Zaban*,a
aDepartment of Chemistry and the Nanotechnology and Advanced Materials Center, Bar Ilan University, Ramat Gan
bDepartment of Chemical Research Support, Weizmann Institute of Science, Rehovot
[email protected], [email protected]
TiO2, a photoactive semiconductor (Eg= 3.2 eV), cannot generate enough current to sustain power in a photovoltaic device due to its limited spectral activity. Typically it is used in conjunction with light absorbing materials that extend the spectral response of the photovoltaic device. Recently, it was shown that plasmonic nanoparticles can inject hot electrons into TiO2 and extend the photovoltaic spectral response. However, in order to obtain these nanoparticles, their formation requires either patterning or special preparation techniques. Furthermore, to complete the solar cell structure usually a hole transport material is used.
We prepared a solid state plasmonic solar cell, based on TiO2 and Ag, without complicated nanoparticle deposition techniques and with no hole transport material. To obtain these solar cells, silver was deposited with different thicknesses by sputtering as a back contact for the solar cells. The silver nanostructures are formed by the rough nature of the TiO2. The Ag has a dual role both as the current conductor and as the metal forming a Schottky barrier. The Ag generates hot electrons upon illumination, injected into the TiO2, enhancing the photovoltaic activity of the solar cells. We provide evidence for the plasmonic photovoltaic activity by performing IPCE measurements that show a current onset at around 700 nm, while XPS reveals a wide-spread plasmonic peak. I-V measurements show photovoltaic activity dependent on the Ag back contact thickness. The best cell performances give short circuit currents of 1.18 mA cm-2 and open circuit voltages of 400 mV. To our knowledge the obtained currents are much higher than any previous report for TiO2/Ag solar cells.
[34] SOLAR ENERGY DRIVEN SOLID STATE FERMENTATION FOR CONTINUOUS FLOW BIOETHANOL PRODUCTION
Betina Tabah1
1 Bar-Ilan University; Department of Chemistry and Bar-Ilan Institute of Nanotechnology and Advanced Materials (Bina)
Betina Tabah, Indra Neel Pulidindi, Aharon Gedanken*
Department of Chemistry and Bar-Ilan Institute of Nanotechnology and Advanced Materials (BINA), Bar-Ilan University, Ramat-Gan 52900, Israel
* Corresponding author:
e-mail: [email protected]
ABSTRACT
The focus of the present research is to develop energy efficient, sustainable, and continuous flow bioethanol production based on solar energy. Solid state fermentation of glucose was performed in a specially designed solar energy driven reactor. Produced ethanol was separated from the yeast bed soon after its formation by an evaporation-condensation process. When aqueous glucose solutions of 10 and 20 wt. % were fed into the reactor bed containing the Baker’s yeast (Saccharomyces cerevisiae), 4.7 and 8.7 wt. % ethanol yields were obtained, respectively. High ethanol yields (91.2 and 85.5 % of the theoretical yield, respectively) indicate the atom efficiency of the process. No loss in the activity of yeast was observed even after two months of continuous operation of the solar reactor. The ethanol produced from 20 wt. % feed (ca. 2 M) was demonstrated as a potential fuel for direct ethanol fuel cells. The use of non-noble metal electrode catalysts for the operation of the fuel cell for electricity generation makes the methodology innovative and economically feasible. Thus, the current study demonstrates an energy efficient methodology for bioethanol production utilizing the solar energy.
[44] SELECTIVE PRODUCTION OF GLUCOSE FROM RICE STRAW USING SOLID ACID CATALYST UNDER MICROWAVE IRRADIATION
Amudhavalli Victor1
1 Bar-Ilan University; Chemistry Department
Amudhavalli Victor, Indra Neel Pulidindi, Aharon Gedanken*
Department of Chemistry and Bar-Ilan Institute of Nanotechnology and Advanced Materials (BINA), Bar-Ilan University, Ramat-Gan 52900, Israel
* Corresponding author:
e-mail: [email protected]
The problems of environmental deterioration as well as energy demands could be alleviated by the paradigm shift to the use of biofuels from fossil fuels. Innovative strategies were developed recently for the exploitation of biomass for biofuels production. A selective, green and fast method for the production of glucose from the rice (Oryza Sativa) straw is demonstrated. Aq. ammonia based pretreatment techniques played a crucial role in the removal of lignin and xylan from rice straw which in-turn accelerated glucan hydrolysis and improved the selectivity of glucose production. The cellulose isolated from rice straw was further hydrolyzed to glucose using a solid acid catalyst (activated carbon supported phosphotungstic acid, 40 wt. % HPW/AC). Microwave irradiation of cellulose from rice straw for a short duration of 5 min. at 100 °C yielded 11.2 wt.% glucose relative to 8 wt.% glucose produced from hydrothermal hydrolysis process (3 h, 150 °C) with a substrate to catalyst wt./wt. ratio of 1. Thus an effective biomass pretreatment (aq. ammonia – dil. H2SO4) method and an accelerated and selective biomass hydrolysis process were developed.
[56] PEROVSKITES FOR PHOTOVOLTAICS IN THE SPOTLIGHT: PHOTOINDUCED PHYSICAL CHANGES AND THEIR IMPLICATIONS
Ronen Gottesman1, Arie Zaban1
1 Bar Ilan University; Bar Ilan University
Perovskites for Photovoltaics in the Spotlight: Photoinduced Physical Changes and Their Implications
Ronen Gottesman* and Arie Zaban
Department of Chemistry, Center for Nanotechnology & Advanced Materials,
Bar-Ilan University, Ramat Gan 52900, Israel.
[email protected]
Organic-inorganic halide perovskites are in consensus to revolutionize the field of photovoltaics and optoelectronic devices due to their superior optical and electronic properties which are unprecedented in comparison to those of other solution processed semiconductors. These hybrid materials are used as light absorbers and also as charge carries which makes them very versatile to be implemented and studied in multitude of fields. Traditionally, the working paradigm in solar cells and optoelectronic devices’ characterization has been that the properties of photovoltaic materials remain stable following illumination of varying times and intensities. However, a growing number of reports on prolonged illumination-dependent physical changes (photoinduced changes) in perovskite films and perovskite based devices. The changes are reversible and range from structural transformations and differences in optical characteristics, to an increase in optoelectronic properties and physical parameters.
We review photoinduced changes in three reported model systems which display changes under prolonged illumination. The systems are: i) a free-standing perovskite film on a glass substrate, ii) a symmetrical system with non-selective electrical contacts, iii) a working perovskite solar cell. The photoinduced changes of each model system are discussed along with the implications on future experimentation design, data analysis and characterization that involve organic-inorganic halide perovskites illumination.
[68] FERROELECTRICITY FOR ALL-OXIDE PHOTOVOLTAICS- STUDY OF BI2O3 AND BIMNO3 FABRICATED BY SPRAY PYROLYSIS
Adam Ginsburg1, David A Keller2, Hannah Noa Barad3, Kevin Rietwyk4, Assaf Anderson4, Arie Zaban4
1 Bar-Ilan University; Anna&max Webb
2 Bar-Ilan University; Bar-Ilan University
3 Bar Ilan University; Department of Chemistry
4 Bar Ilan University; Bar Ilan University
Recently, ferroelectric materials draw significant interest as possible materials for photovoltaics. This is due to their unique property – Its ability to remain polarized after the application of an external electric field. This property was reported to allow an internal electric filed that drives charge separation within a single material, as opposed to p-n heterojunction, where the field is formed in the junction between two materials.
In this work, spray pyrolysis of Bi2O3 and BiMnO3, both reported ferroelectric materials, were fabricated by spray pyrolysis and were tested for their photovoltaic properties both as a single materials, and in a junction configuration. So far reaching a voltage higher than 1.1V. In addition, a full characterization of the film is performed in order to discover the crystal phase (XRD), and the optical properties of the film.
[71] OXIDE ABSORBER MATERIALS FOR ALL-OXIDE PHOTOVOLTAICS
Koushik Majhi1
1 Bar Ilan Institute of Nanotechnology and Advanced Materials (Bina); Bar-Ilan
Oxide Absorber materials for All-Oxide Photovoltaics
Koushik Majhi*, Assaf Anderson, Hannah-Noa Barad, Kevin Rietwyk, Adam Ginsburg, David Keller, Yaniv Bouhadana, Zhi Yan, Eli Rosh-Hodesh, Arie Zaban
* Presenting author. E-mail: [email protected]
Combinatorial synthesis in conjunction with high-throughput (HT) methods have been developed to synthesize novel thin-film absorber materials for low cost all oxide photovoltaics.1 Most metal oxides (MOs) have a bandgap in the UV part of the solar spectrum and it is the aim of the project to synthesize and identify novel multi-component MOs with a band gap at lower energies. Continuous compositional spreads of metal oxides were synthesized via pulsed laser deposition (PLD) and high throughput techniques were used to study optical structural, optical and electrical properties as a function of composition. The optical transmission spectra of mixed multi-component metal oxides show enhanced light absorption in the visible range. The crystal structure as a function of composition was characterized using scanning XRD and Raman spectroscopy. Application of such light absorbers in PV devices show improved performance compared to the pure metal oxide components of the absorber.
References:
1. Rühle, S.; Anderson, A. Y.; Barad, H.-N.; Kupfer, B.; Bouhadana, Y.; Rosh-Hodesh, E.; Zaban, A. All-Oxide Photovoltaics. J. Phys. Chem. Lett. 2012,3, 3755–3764
[84] MAGNETISM IN OLIVINE-TYPE LICO1-XFEXPO4 CATHODE MATERIALS: BRIDGING THEORY AND EXPERIMENT
Yelena Gershinsky1, David Zitoun2
1 Bar Ilan Institute of Nanotechnology and Advanced Materials (Bina); Bar Ilan Institute of Nanotechnology and Advanced Materials (Bina)
2 Bar Ilan University; Chemistry and the Institute for Nanotechnology and Advanced Materials, Bar-Ilan University
Magnetism in Olivine-type LiCo1-xFexPO4 Cathode Materials: Bridging Theory and Experiment
Yelena Gershinsky § and David Zitoun*
Vijay Singh,§ Monica Kosa, Mudit Dixit, Dan Thomas Major*
Department of Chemistry and the Lise Meitner-Minerva Center of Computational Quantum
Chemistry and the Institute for Nanotechnology and Advanced Materials, Bar-Ilan University
§ Equal contribution
* Electronic mail: [email protected], [email protected]
In the current work, we present a non-aqueous sol-gel synthesis of olivine type LiCo1-xFexPO4 compounds (x = 0.00, 0.25, 0.50, 0.75, 1.00). The magnetic properties of the olivines are measured experimentally and calculated using first-principles theory. Specifically, the electronic and magnetic properties are studied in detail with standard density functional theory (DFT), as well as by including spin-orbit coupling (SOC), which couples the spin to the crystal structure. We find that the Co2+ ions exhibit strong orbital moment in the pure LiCoPO4 system, which is partially quenched upon substitution of Co2+ by Fe2+. Interestingly, we also observe a non-negligible orbital moment on the Fe2+. We underscore that the inclusion of SOC in the calculations is essential to obtain qualitative agreement with the observed effective magnetic moments. Additionally, Wannier functions were used to understand the experimentally observed rising trend in the Néel temperature, which is directly related to the magnetic exchange interaction paths in the materials. We suggest that out of layer M – O – P – O – M magnetic interactions (J⊥) are present in the studied materials. The current findings shed light on important differences observed in the electrochemistry of the cathode material LiCoPO4 compared to the already mature olivine material LiFePO4.
(Paper submitted to Physical Chemistry Chemical Physics)
[100] A LAYERED-SPINEL COMPOSITE CATHODE LINI0.33MN0.54CO0.13O2 WITH VERY GOOD CYCLING STABILITY FOR LI-ION BATTERIES
Prasant Nayak1, Judith Grinblat1, Mikhael Levi1, Elena Levi1, Doron Aurbach1
1 Bar-Ilan University; Bar-Ilan University
A layered-spinel composite cathode LiNi0.33Mn0.54Co0.13O2 with very good cycling stability for Li-ion batteries
Prasant Kumar Nayak, Judith Grinblat, Mikhael Levi, Elena Levi, Doron Aurbach*
Department of Chemistry, Bar-Ilan University, Ramat-Gan, Israel 5290002
Abstract
A layered-spinel composite LiNi0.33Mn0.54Co0.13O2 is synthesized by self-combustion reaction (SCR) and studied as a cathode material for Li-ion batteries. The Rietveld analysis of LiNi0.33Mn0.54Co0.13O2 indicates the presence of monoclinic Li[Li1/3Mn2/3]O2 (31%) and rhombohedral (LiNixMnyCozO2) (62 %) phases as the major components with spinel (LiNi0.5Mn1.5O4) (7 %) as a minor component, which is well supported by TEM and electron diffraction. Its electrochemical performance is compared with that of the layered cathode material LiNi0.33Mn0.33Co0.33O2 in a wide potential window of 2.3-4.9 V vs. Li/Li+. A discharge specific capacity of about 170 mAh g-1 is obtained in the potential range of 2.3-4.9 V vs. Li at low rate (C/10) with excellent capacity retention upon cycling. On the other hand, LiNi0.33Mn0.33Co0.33O2 (NMC111) synthesized by SCR exhibits an initial discharge capacity of about 208 mAh g-1 in the potential range of 2.3-4.9 V, which decreases to a value of 130 mAh g-1 after only 50 cycles. Thus, the presence of spinel in multiphase structure of LiNi0.33Mn0.54Co0.13O2 seems to stabilize the behavior of this cathode material even when polarized to high potentials. The excellent cyclability of LiNi0.33Mn0.54Co0.13O2 can be ascribed to the suppression of layered-to-spinel phase transformation due to presence of a spinel component LiNi0.5Mn1.5O4 in the pristine active mass. Also, LiNi0.33Mn0.54Co0.13O2 shows superior retention of average discharge voltage upon cycling as compared to LiNi0.33Mn0.33Co0.33O2 when cycled in such a wide potential range.
[103] PHOTO-INDUCED REVERSIBLE STRUCTURAL TRANSFORMATIONS IN FREE STANDING CH3NH3PBI3 PEROVSKITE FILMS
Ronen Gottesman1, laxman gouda1, Basanth S. Kalanoor1, Eynav Haltzi1, Shay Tirosh1, Eli Rosh Hodesh2, Yaakov Tischler3, Arie Zaban1, Claudio Quarti4, Filippo De Angelis4
1 Bar Ilan University; Bar Ilan University
2 Dept. Chemistry; Nanotechnology
3 Bar-Ilan Institute of Nanotechnology and Advanced Materials; Bar-Ilan University
4 Computational Laboratory for Hybrid/Organic Photovoltaics (Clhyo); Computational Laboratory for Hybrid/Organic Photovoltaics (Clhyo)
Abstract:
In the pursuit to better understand the mechanisms of perovskite solar cells we performed Raman and Photoluminescence measurements of free standing CH3NH3PbI3 films, comparing dark with working conditions. The films, grown on a glass substrate and sealed by a thin glass cover slip, were measured subsequent to dark and white light pretreatments. The extremely slow changes we observe in both the Raman and Photoluminescence cannot be regarded as electronic processes which are much faster. Thus, the most probable explanation is of slow photo-induced structural changes. The CH3NH3PbI3 transformation between the dark and the light structures is reversible, with faster rates for the changes under illumination. The results seem to clarify several common observations associated with solar cell mechanisms, like performance improvement under light soaking. More important is the call for solar cell related investigation of CH3NH3PbI3 to take the photo-induced structural changes into consideration when measuring and interpreting the results.
[104] UNRAVELING OPPOSING OPERATING MECHANISMS IN MULTI-LAYERED ALL-OXIDE PHOTOVOLTAIC CELLS
David A Keller1, Koushik Majhi2, Kevin Rietwyk3, Adam Ginsburg4, Hannah Noa Barad5, Zhi Yan3, Yaniv Bouhadana6, Eli Rosh Hodesh6, Assaf Anderson3, Arie Zaban3
1 Bar-Ilan University; Bar-Ilan University
2 Bar Ilan Institute of Nanotechnology and Advanced Materials (Bina); Bar-Ilan
3 Bar Ilan University; Bar Ilan University
4 Bar-Ilan University; Anna&max Webb
5 Bar Ilan University; Department of Chemistry
6 Dept. Chemistry; Nanotechnology
Unraveling Opposing Operating Mechanisms in Multi-layered All-Oxide Photovoltaic Cells
David A Keller, Koushik Majhi, Kevin J. Rietwyk, Adam Ginsburg, Hannah-Noa Barad, Zhi Yan, Yaniv Bouhadana, Eli Rosh-Hodesh, Assaf Y Anderson and Arie Zaban
Chemistry department and the center for nanotechnology and advanced materials, Bar-Ilan University, Ramat-Gan, Israel, 5290002
[email protected]
A promising family of photovoltaic solar cells, based solely on metal oxide thin films, has recently been gaining interest. To improve the inadequate electrical properties of the pure metal oxide materials, various metal oxides are mixed, to create new composite materials that may exhibit enhanced properties. The new materials are then examined as light absorbing layers in photovoltaic cells, stacked between other metal oxide layers in multi-layered structure. The structure is consisting of different metal oxide layers: transparent conductive layer, electron transport layer, absorber layer and hole transport layer. Because of the multi-layered structure, it is difficult to resolve the operating mechanism of these solar cells.
To meet this need, a home-built high-throughput incident photon to current efficiency (IPCE) measuring system was constructed. Using the new system and other high-throughput optical, electrical and structural scanning systems, we thoroughly studied the operating mechanisms of several all-oxide samples, including composite materials of Fe2O3, Co3O4, Bi2O3, TiO2 and others. In many of the cells we found evidence for two distinct processes with different operating mechanisms. The two mechanisms may work in parallel, compete, or even counter each other. As for their origin, the two mechanisms may result from photovoltaic activity of two different layers, or alternatively from activity of two separate bandgaps within the same material.
Once the different mechanisms are understood, it is possible to enhance or to suppress one of them. This will allow for further improvement of the all-oxide cells’ photovoltaic performance.
[111] THE EFFECT OF ORGANIC LIGANDS ON SI NANOPARTICLES AS ANODE MATERIAL FOR LI ION BATTERY
Gal A Grinbom1
1 Bar Ilan University; Bar Ilan University
The effect of Organic ligands on Si Nanoparticles as anode material for Li ion battery
Gal Grinbom and David Zitoun
Department of Chemistry, Bar Ilan Institute of Nanotechnology and Advanced Materials (BINA), Ramat Gan 52900, Israel
Batteries are valuable electrochemical cells and play an important role in the green energy strategies. Typical Electrochemical cell is composed of many components that affect each other. In this study, we focus on understanding the contribution of organic ligands decorating Si nanoparticles (NPs) surface. These Organic ligands can affect: the solid-electrolyte interface (SEI) formation, the insertion of the Li ion into the Si and improve the conductivity of the anode.
In order to decorate Si NPs surface with organic ligands, octyne, perfluorooctyne and triethoxy(octyl)silan are used. The resulting materials are fully characterized by electrochemical measurements. In general, we have found that the octyne treatment doesn’t affect the electrochemical properties. Moreover, since the fluoro-organic layer on the Si NPs changes the connection to the SEI, the Perfluorooctyne treatment has decreased the capacity and cycle ability of the Si anode due to the formation of wide cracks on the anode.
.
Figure: from right to left, Si NPs after perflorooctyne, octyne and triethoxy(octyl)silan treatment.
[112] INORGANIC CSPBBR3 PEROVSKITE TYPE SOLAR CELL PHOTOVOLTAGE CHARACTERIZATION
Jiangang Hu1, laxman gouda1, Ronen Gottesman1, Adi Kama1, Adam Ginsburg2, David A Keller3, Shay Tirosh1, Eli Rosh Hodesh4, Yaniv Bouhadana4, Arie Zaban1
1 Bar Ilan University; Bar Ilan University
2 Bar-Ilan University; Anna&max Webb
3 Bar-Ilan University; Bar-Ilan University
4 Dept. Chemistry; Nanotechnology
Abstract: Hybrid organic-inorganic metal halide perovskites have drew much attention over the past 5 years due to their amazing optoelectronic properties and promising application in energy field. However, compared to hybrid organic−inorganic perovskites, the all-inorganic metal halide perovskites are less studied in the field of solar cells. The inorganic CsPbBr3 perovskite was implemented in solar cell and working as good as its organic counterparts especially in generation of phtovoltage. Here, we have fabricated inorganic CsPbBr3 perovskite type solar cell by sequential deposition method. The photovoltage behavior was studied as a function of light intensity and transient photovoltage decay measurements in both mesoporous and planar structured devices. We discussed the recombination pathway from TiO2 and CsPbBr3 perovskite interface and the long carrier life time due to slow recombination in mesoporous structured device. However, planar structured device showing shorter carrier life time or fast recombination of carriers which may happens in perovskite.
[115] RECENT ADVANCES IN THE PRODUCTION OF BIOETHANOL – A RENEWABLE AND ALTERNATE FUEL
Indra Neel Pulidindi1, Aharon Gedanken1
1 Bar-Ilan University; Department of Chemistry
Recent Advances in the Production of Bioethanol – a Renewable and Alternate Fuel
Indra Neel Pulidindia & Aharon Gedankena,b
aDepartment of Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
bNational Cheng Kung University, Department of Materials Science and Engineering, Tainan 70101, Taiwan
Tel: +972-3-5318315; Fax: +972-3-7384053;
*E-mail: [email protected]
Innovative strategies were developed recently for the exploitation of biomass for biofuels production. The concept of biomass itself is being understood in an unconventional sense. Biofuel production strategies are also undergoing drastic changes like the use of solar radiation and microwave irradiation, to meet the fuel demand and to make the process more energy and atom efficient and sustainable.
With the above scientific and technological research background, we have focused on making advances in the first (corn and sugar cane), second (cellulose) and third (algae) generation bioethanol production. First generation bioethanol has already reached the level of commercialization but facing the problem of food Vs fuel conflict. To make this process more profitable we have developed a solar energy driven reactor for the simultaneous saccharification and fermentation (SSF) of starch to bioethanol and demonstrated its applicability in driving fuel cells for electricity generation. Similarly, in the field of second generation bioethanol production, effective utilization of all the components of biomass, especially xylose metabolism is a challenge. We demonstrated the feasibility of xylose metabolism, produced from the hydrolysis of pinus radiata cones, by saccharomyces cerevisiae. With respect to the third generation bioethanol production, we have cocultured the marine algae ulva rigida under nutrient rich conditions where fish were fed, so as to produce carbohydrate rich algae. Subsequently, we have developed a sonication assisted SSF process for the conversion of the high carbohydrate ulva rigida (32 wt. % starch) to bioethanol in high yield (16 wt.% on dry weight basis). All these developments would be discussed in the Nano Israel 2016.
[118] ENHANCING DEVICE PERFORMANCE: PLASMONIC NANO-ANTENNAS FOR LIGHT EMISSION, DETECTION AND HARVESTING.
Ofir Sorias1
1 Technion; Electrical Engineering
Enhancing Device Performance: Plasmonic Nano-Antennas for Light Emission, Detection and Harvesting
Ofir Sorias* and Meir Orenstein.
Department of Electrical Engineering, Technion – Israel Institute of Technology, 32000 Haifa, Israel.
[email protected]
Abstract: We experimentally demonstrate performance enhancement in detectors, solar-cells and light-emitting diodes, by utilizing plasmonic nanostructures and their localized surface plasmon resonances. We derive design rules for such plasmonic nanostructures – and plasmonic nano-antennas in particular – by investigating their plasmonic properties, and their effects on the emission and absorption capabilities of neighboring materials.
Plasmonic nano antennas (PNA) have been thoroughly investigated in recent years, since their localized surface plasmon resonances (LSPR) enables high field concentration and enhancement. LSPR can increase the local density of photonic states and therefore affect light-matter interactions.
Here we experimentally demonstrate how, with proper design, LSPR can modify absorption and emission processes, and enable new and interesting transitions by manipulating light-matter interactions – thereby achieving better device performance.
Figure 1 shows scanning electron microscope images of several PNAs (a), alongside measured reflection as a function of wavelength (b,c) for two such antennas (red arrows). They exhibit a LSPR accompanied by a corresponding field enhancement (inset, simulated).
Figure 2 shows various plasmonic nanostructure designs enhancing measured performance in three types of devices: a detector with improved responsivity (a), a solar-cell with better efficiency (b), and a light emitting diode with faster modulation times and improved light extraction (c).
[1] A. Pesach, S. Sakr, E. Giraud, O. Sorias, L. Gal, M. Tchernycheva, M. Orenstein, N. Grandjean, F. H. Julien, and G. Bahir, First demonstration of plasmonic GaN quantum cascade detectors with enhanced efficiency at normal incidence, Optics Express 22, 21069 (2014).
[2] T. Segal-Peretz, O. Sorias, M. Moshonov, I. Deckman, M. Orenstein, G. L. Frey, Plasmonic nanoparticle incorporation into inverted hybrid organic–inorganic solar cells, Organic Electronics 23, 144 (2015).
[137] HIGH POWER CONVERSION EFFICIENCY OF FTO|TIO2|CUXO|AU SOLAR CELLS
Zhi Yan1, Jiangang Hu2, Adam Ginsburg3, Shay Tirosh1, Kevin Rietwyk1, Koushik Majhi4, Assaf Anderson1, Arie Zaban1
1 Bar Ilan University; Bar Ilan University
2 Chemistry Department; Chemistry Department
3 Bar-Ilan University; Anna&max Webb
4 Bar Ilan Institute of Nanotechnology and Advanced Materials (Bina); Bar-Ilan
High power conversion efficiency of FTO|TiO2|CuxO|Au solar cells
Abstract: Cu-O layer, as an absorber, has been researched in many photovoltaic applications, due to its tunable bandgap from 1.4 to 2.1 eV. Although there are reports in the literature on its power conversion efficiency using heterojunctions of Cu2O and ZnO or Ga2O3, these employ an opaque substrate of Cu sheet or Si wafer and which limits possible device architectures, at a higher device cost. Here we use an inexpensive transparent substrate of glass coated with FTO and deposit a TiO2 layer using spray pyrolysis, followed by an electrochemical CuxO deposition – each of the materials and processing steps are low cost and can readily be up-scaled for module fabrication. Detailed characterization on our cells reveal a high power conversion efficiency above 1% with a high short circuit current density of 5 mA/cm2, open circuit voltage of 500 mV and fill factor of 40%.
[164] DESIGNING EFFICIENT BIMETALLIC PHOTOCATALYSTS FOR HYDROGEN PRODUCTION
eran aronovitch1, Philip Kalisman2, Shai Mangel3, Lothar Houben4, Lilac Amirav5, Maya Bar Sadan6
1 Chemistry Department, Ben Gurion University of the Negev, Beer Sheba, Israel; Chemistry Department, Ben Gurion University of the Negev, Beer Sheba, Israel
2 Technion – Israel Institute of Technology; Technion – Israel Institute of Technology
3 Ben Gurion University; Ben Gurion University
4 Weizmann Institute of Science; Weizmann Institute of Science
5 Technion – Israel Institute of Technology ; Technion – Israel Institute of Technology
6 Ben Gurion University ; Ben Gurion University
Designing efficient bimetallic photocatalysts for hydrogen
production
Eran Aronovitch1, Philip Kalisman2, Shai Mangel1, Lothar Houben3, Lilac Amirav2, Maya Bar-Sadan1*
1 Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel
2 Schulich Faculty of Chemistry, The Russell Berrie Nanotechnology Institute, and The Nancy and Stephen Grand Technion Energy Program; Technion − Israel Institute of Technology, Haifa 32000, Israel
3 Peter Grünberg Institut 5 and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
The search for alternative clean and renewable energy source is a major pressing issue. One promising direction is the use of semiconductor nanoparticles as photocatalysts which absorb the solar radiation and produce hydrogen from water. Efficient photocatalysts should maintain charge separation of the holes and electrons and contain different sites for oxidation and reduction. Usually metallic particles are deposited on the semiconductors which acts as electron sinks and a reduction sites for protons.
Hybrid core-shell structures such as CdS@CdSe increase the charge separation and reduce the particle dissolution by confining the holes to the core and leaving the electrons delocalized over the entire structure. A bi-metallic co-catalyst composed of metals such as gold and palladium should improve the photocatalytic activity of the system. Such bimetallic particles possess the ability to attract electrons from the semiconductor and discharge them into the aqueous solution more efficiently then each of the metals separately. Here we use the CdSe@CdS-Au\Pd system as a case study to explore the effect of the inner structure of the bimetallic tip on the photocatalytic performance. In addition we study the dynamic processes which occur during photocatalysis. For this aim we used high resolution energy dispersive spectroscopy (EDS) for the system characterization and an online GC equipped setup for the long duration photocatalytic hydrogen evolution measurements.
*Aronovitch, E.; Kalisman, P.; Mangel, S.; Houben, L.; Amirav, L.; Bar-Sadan*, M.; Designing Bimetallic Co-catalysts: A Party of Two. J. Phys. Chem. Lett. 6, 3760 (2015)
[196] TISSUE-LIKE SILICON NANOWIRES-BASED 3D ANODES FOR HIGH-CAPACITY LITHIUM ION BATTERIES
Emanuel Peled1, Fernando Patolsky1, Diana Golodnitsky2, Kathrin Freeedman1, Guy Davidi1, dan Schneier1
1 School of Chemistry; School of Chemistry
2 Honeycomb Batteries Ltd; Tel Aviv University
Tissue-like Silicon Nanowires-based 3D Anodes for High-Capacity Lithium Ion Batteries
Emanuel Peled1, Fernando Patolsky1, Diana Golodnitsky1, 2, Kathrin Freedman1, Guy Davidi1, Dan Schneier1
1. School of Chemistry, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
2. Applied Materials Research Center, Tel Aviv University, Tel Aviv, 69978, Israel.
Abstract
We report on the scalable synthesis and characterization of novel architecture three-dimensional high-capacity amorphous SiNWs-based anodes, with focus on studying their electrochemical degradation mechanisms. We achieved an unprecedented combination of remarkable performance characteristics, high loadings of 3-25 mAh/cm2, a very low irreversible capacity (10% for the 3-4 mAh/cm2 anodes), current efficiency greater than 99.5%, cycle stability both in half cells and a LiFePO4 battery and fast charge–discharge rates (up to 2.7C at 20mA/cm2). These SiNWs-based binder-free 3D anodes have been cycled for over 500 cycles, exhibiting a stable cycle life. Notably, it was found that the growth of the continuous SEI layer thickness, and its concomitant increase in resistivity, represents the major reason for the observed capacity loss of the SiNWs-based anodes, as we demonstrate by cleaning and reusing cycled anodes. We have recently begun experimenting with different types of coatings to further improve SEI and cycling stability. Our data reveal that NWs-based anodes of novel architecture are expected to meet the requirements of lithium-ion batteries for both portable and electric-vehicle applications.
[204] LIMITING NON RADIATIVE PATHWAYS IN ORGANIC-INORGANIC PEROVSKITE SOLAR CELLS USING A P3HT NANOWIRES–PMMA BLEND AS AN EFFICIENT AND CHEAP HOLE‐TRANSPORTER
Alba PELLAROQUE1
1 University of Oxford; University of Oxford
From a stability point of view, an ideal Hole Transporter Material (HTM) would protect the perovskite from ambient moisture while still ensuring effective charge transfer and transport. Moreover, to achieve a perfect solar cell, the desired contact must not induced any nonradiative decay channels at open circuit conditions, maximizing the attainable photovoltage. In the case of the perovskites solar cells, all contacts used induce a non-radiative decay channel across the contact-semiconductor interface. Holes in the HTM recombine with electrons in perovskite, explaining the extreme photoluminescence quenching thus far always observed at perovskites – HTM interfaces. Hence, the ideal HTM is one that can perform the multiple tasks of being hole-selective, protecting the semiconductor from ambient conditions, without impeding but perhaps even improves radiative recombination yields in the semiconductor – HTM composite.
We developed a dopant free hole-transporter composite by blending P3HT nanowires semiconducting polymer with insulating PMMA. Such blend shows high increase in open circuit voltage suggesting a drastic reduction of non-radiative recombination decay channels, as well as improves stabilized efficiency compared to the pristine P3HT. Interestingly, the PMMA/P3HT-NWs composite hole-conductor seems to operate through a very different mechanism than any other currently known HTMs. We propose that upon light excitation, holes are rapidly transferred from the absorber to the nanowires, where they reside with long lifetimes and then transfer back to the valence band of the perovskite. Then, holes recombine radiatively leading to a large enhancement in photoluminescence yield.
[206] NOVEL EXOHEDRAL NANOCARBON HYBRID STRUCTURE: CARBON NANOTUBE COATED BY FULLERENE SHELL
Eugene Katz1
1 Ben-Gurion University of the Negev; J. Blaustein Institute for Desert Research
Novel Exohedral Nanocarbon Hybrid Structure: Carbon Nanotube Coated by Fullerene Shell
Leonid A. Chernozatonskii,a Anastasiya A. Artyukh,a Victor A. Demin,a
Eugene A. Katzb,c,*
a. Emanuel Institute of Biochemical Physics, RA S, Moscow,119334 Russia
b. Dept. of Solar Energy and Environmental Physics, The Jacob Blaustein Institutes for Desert Research (BIDR), Ben-Gurion University of the Negev, Sede Boker Campus 84990, Israel
c. Ilse Katz Institute for Nanoscale Science & Technology, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
* Corresponding author, e-mail: [email protected]
Can a C60 layer cover a surface of single-wall carbon nanotube (SWCNT) forming an exohedral pure-carbon hybrid with only van der Waals (VdW) interactions? The aim of the present work is to address this question and to demonstrate that the fullerene shell layer in such a bucky-corn structure can be stable. Theoretical study of the structure, stability and electronic properties of bucky-corn hybrids is reported for the shell of C60 and C70 molecules on an individual SWCNT, C60 dimers on an individual SWCNT, as well as C60 molecules on SWNT bundles. The geometry and total energies of the bucky-corns were calculated by the molecular dynamics method while the density functional theory method was used to simulate the electronic band structures [1].
References
1. L. A. Chernozatonskii, A. A. Artyukh, V. A. Demin and E. A. Katz, Molecular Physics (2015), in press. DOI: 10.1080/00268976.2015.1086834.
[236] HYBRID CDS-AU NANORODS AS PHOTOCATALYSTS; SURFACE COATING AND METAL DOMAIN SIZE EFFECTS.
Yuval Ben Shahar1
1 The Institute of Chemistry and Center for Nanoscience and Nanotechnology; The Hebrew University of Jerusalem
Water reduction for hydrogen production by semiconductor-metal hybrid nanoparticles (HNPs) has been considered a promising approach towards renewable solar energy harvesting in form of chemical energy stored in a hydrogen fuel. The synergistic optical and chemical properties of HNPs such as light-induced charge separation and charge transfer, allow photocatalytic activity which can promote surface chemistry redox reactions. Control over components materials, shape, size and surface coating permits fine tuning of wavelength absorption range, energy band alignment and surface traps suppression which are key-factors for efficient charge transfer and overall catalysts activity.
Here we report on the effects of the surface coating and the co-catalyst metal size on the photocatalytic function of Au tipped CdS nanorods as a model hybrid nanoparticle system. Both tested parameters were found to influence the photocatalytic efficiency and charge transfer dynamics. Different types of surface coatings including various types of thiolated alkyl ligands and different polymer coatings were explored. A significant increase in the apparent quantum yield was detected for polyethylenimine (PEI) coated NPs compared to other surface coatings, such as L-Glutathione and mercaptoundecanoic acid. This pronounced increase in the photocatalytic efficiency is attributed to the improved surface passivation by the PEI polymer reducing the surface trapping of charge carriers, compared to alternative surface coatings. Investigation of different sizes of Au metal component reveal an optimum behavior in which an intermediate size of metal domain provides the optimal hydrogen evolution rate for the photocatalytic water reduction while smaller sized Au tips show slower rates and lower efficiency and larger sizes expose also lower rates and reduced apparent quantum yield. Ultrafast transient absorbance measurements in collaboration with Cerullo’s Group from POLMI along with steady-state emission and time-resolved spectral measurements support these observations. The understanding of the effect of the hybrid nanosystems properties on the photocatalytic processes contributes to the great potential of hybrid nanostructures photocatalytic applications.
[263] IMPACT OF ANTI-SOLVENT TREATMENT ON CARRIER DENSITY IN EFFICIENT HOLE CONDUCTOR FREE PEROVSKITE BASED SOLAR CELLS
Bat-El Cohen1
1 The Hebrew University of Jerusalem; The Hebrew University of Jerusalem
Impact of anti-solvent treatment on carrier density in efficient hole conductor free perovskite based solar cells
Bat-El Cohen, Sigalit Elboher, Alex Dymshits, Lioz Etgar*
The Hebrew University of Jerusalem, Jerusalem 919040, Israel
Recently organic-inorganic perovskite has attracted lot of attention due to its properties, which are suited to photovoltaic (PV) solar cells. The efficiency of perovskite-based solar cells has increased in a short time, achieving today 20.1% [1]. It was demonstrated that the perovskite could function simultaneously as light harvester and hole conductor, simplifying the solar cell structure and potentially reducing its cost. This work demonstrates anti-solvent treatment of organo-metal halide perovskite film. We found that the anti-solvent (toluene) surface treatment affects the morphology of the perovskite layer, and importantly it also affects the electronic properties of the perovskite. One of the most discussed phenomena in the field of perovskite-based solar cells is the hysteresis effect. It has been demonstrated that hysteresis is present in the perovskite solar cells, and hysteresis is heavily dependent on the solar cell structure as well as on the scan velocity during current voltage (IV) measurements [2]. Conductive atomic force microscopy (cAFM) and surface photovoltage show that the perovskite film becomes more conductive after the antisolvent treatment. Moreover, the anti-solvent treatment suppresses the hysteresis commonly obtained for perovskite-based solar cells. When characterizing the perovskite only, an IV plot of a single perovskite grain measured by cAFM shows that the hysteresis vanishes after the toluene treatment.
We postulated that during the toluene treatment, the excess of charges on the perovskite surface is removed, leading to a stable and naturalized perovskite crystal. As a result of the anti-solvent surface treatment, a hole conductor free, perovskite-based solar cell demonstrates impressive power conversion efficiency of 11.2%.
References
[1] http://www.nrel.gov/ncpv/images/efficiency_chart.jpg.
[2] Snaith, H. J. et al. J. Phys. Che. Lett., 2014, 5, 1511−1515.
[275] INORGANIC LAYERED MATERIALS AS CHARGE TRANSPORT LAYERS IN LEAD HALIDE BASED PEROVSKITE SOLAR CELLS
Peter Topolovšek1, Francesco Lamberti1, Chen Tao1, Victor Vega Mayoral2, Matej Prijatelj2, Christoph Gadermaier2, Annamaria Petrozza1
1 Center for Nanoscience and Technology, Istituto Italiano DI Tecnologia; Via Pascoli 70/3
2 Jožef Stefan Institute; Jamova Cesta 39
The performance leap of hybrid organic-inorganic perovskite solar cells can be ascribed to many factors, for example smart processing and deposition techniques, research on alternative metal halide compounds and the advancement in the synthesis of charge transport materials. However, the use of charge transport materials is often limited to organic polymers and small molecules which are commonly dissolved in chlorinated solvents that are not considered environmentally friendly. Recently it has been shown that the use of their inorganic counterparts show better solar cell stability over time, but it still requires high temperature deposition processing1. In this work we examine the charge transfer interface between exfoliated semiconducting inorganic layered materials, such as MoS2 and WS2, and methylammonium lead halide perovskites. The advantages of presented layered materials originate from their simple and scalable exfoliation methods2, ease of processing and doping techniques3, as well as the ability to deposit them in a form of ultra thin films which conform to the active layer surface4. In terms of device construction this results in scalable deposition and, due to the quasi 2D nature of materials, in significant reduction of material consumption. In addition, we use doping in solution to tune the properties of layered materials affecting the series resistance of the device and have control over the band alignment between the active and charge selective layer.
References:
1. W. Chen, et al. Efficient and stable large-area perovskite solar cells with inorganic charge extraction layers. Science, 29 October 2015 (10.1126/science.aad1015)
2. R. J. Smith, et al. Large-scale Exfoliation of Inorganic Layered Compounds in Aqueous Surfactant Solutions. Adv. Mater. 23, 3944–3948 (2011).
3. Y. Shi. et al. Selective Decoration of Au Nanoparticles on Monolayer MoS2 Single Crystal. Sci. Rep. 3, 1839 (2013).
4. X. Yu, M.S. Prévot, N. Guijarro and K. Sivula. Self-assembled 2D WSe2 thin films for photoelectrochemical hydrogen production. Nat. Comm. 6, 7596 (2015).
[295] DEVELOPMENT OF ORGANIC MATERIALS FOR PEROVSKITE SOLAR CELLS
Jeroen van der Velden1
1 Via Morego 30, 16163; Via Morego 30, 16163
Abstract: Perovskite solar cells are a promising class of solar cells due its low-cost solution processing and high power-conversion efficiencies close to 20% approach that of crystalline Si solar cells at lab scale. In such scenario their low long-term stability represent a crucial issue to get to the market.
Here we address such issue both working on the active material and on the device architecture where it is embodied.
The standard device architecture for Perovskite solar cells, also known as the direct architecture is TCO/TiO2/Perovskite/HTM/Au. In this architecture TiO2 works as an electron-extracting layer but is instable upon UV exposure, which can have a detrimental effect on long-term stability. To avoid this issue, the inverted architecture could be used with TCO/PEDOT: PSS/Perovskite/PCBM. The drawback of this architecture is the long-term stability and parasitic absorption of PEDOT: PSS.
An alternative approach is to use PCBM in a direct architecture as an electron-extracting layer. Due to the solubility of PCBM in DMF the perovskite layer has to be deposited in 2 steps by evaporation of PbI2 and spin coating of methylammonium iodide. To avoid the problem of solubility, cross-linkable C61-fullerene derivative was synthesized which can be cross-linked by heating, and could be a good candidate to make it possible to prepare solution process able devices with C61-fullerene derivatives.
On the surface of the active material (perovskite), different kinds of defect sites are present with energy levels close to the conduction band edge. These defect sites (such as under-coordinated Pb atoms) might lead to trap sites, which have a negative influence on the device efficiency and the mobility of defects seems to be emerging as the primary cause of electrical instability often observed in these solar cells. To fill up these defect sites we have designed different kinds of passivation materials for the surface treatment of the perovskite. By successful treatment of defect sites we expect an increase in PCE and long-term stability.
[309] ROLE OF EXTRACTING [6,6]-PHENYL-C61-BUTYRIC ACID METHYL ESTER (PCBM) INTERLAYER IN PEROVSKITE SOLAR CELLS IN THE LIGHT OF MOVING IONS
Vijay Venugopalan1, Annamaria Petrozza2, Francesco Lamberti2, Chen Tao2
1 Center for Nanoscience and Technology,; Istituto Italiano DI Tecnologia
2 Center for Nanoscience and Technology, Istituto Italiano DI Tecnologia; Via Pascoli 70/3
Abstract: In the last few years hybrid organic-inorganic metal halide perovskites have proven to be genuine challengers for traditional technologies in the field of solar cells and display technologies. Such rapid growth in efficiencies of solar cells has been unprecedented for any generation of solar technology. One of the major challenges facing us is to tackle the problem of stability in these solar cells, the origins of which are presently poorly understood. One school of thought points towards ionic motion in these semiconductors to be the key factor. Presently the mechanism of ionic motion in these cells and their effect on neighboring charge extracting layers is poorly understood. Herein we take a closer look at the interaction between the moving iodine(I-) ions in perovskites and the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) interlayer that are widely used in perovskite solar cells. We also observe permanent changes with light soaking in both types of cell. Through Electrochemical Impedance Spectroscopy (EIS) we observe that cells with PCBM interlayers show larger capacitances after light soaking over all relevant frequency ranges. This is in contrast with devices lacking PCBM interlayers where the overall impedance drastically reduces after light soaking. The reverse bias Schottky rectification also improves with light soaking for cells with the PCBM interlayers and weakens for cells without PCBM, pointing towards a permanent change to the interface due to PCBM. In conclusion, we propose that the interaction of the moving I- ions with the PCBM permanently change the electron extraction interface of solar cells, which may be one of the chief responsible factors responsible for the stabilized efficiency and smaller hysteresis observed in these cells.
[313] INVERTED AND STANDARD ARCHITECTURE PEROVSKITE SOLAR CELLS: IMPACT OF NIO AND TIO2 BLOCKING LAYERS DEPOSITION TECHNIQUE
Ralf Niemann1
1 University of Bath; Claverton Down
ABSTRACT:
Methylammonium lead halide perovskites (CH3NH3PbX3; X = Cl, Br, I) are hybrid organic-inorganic materials with a perovskite crystal structure and are a promising candidate in next-generation solar cells. After their first employment in photovoltaics in 2009 with an efficiency of 3.9 % (Kojima et al.) they experienced a fast increase to a certified efficiency of currently to over 20 % (NREL).
In this work we analyze the impact of different types of blocking layers on the operation and performance of perovskite solar cells. Classical perovskite cells were fabricated based on an n-type TiO2 electron blocking layer and were compared to organic n-type layers. Because the processing can influence the work function of the resulting blocking layer we employed three different deposition techniques of TiO2 and compared their function as an efficient electron extraction layer. On the other hand, perovskite solar cells with an inverted structure were fabricated, where the bottom layer was based on a p-type NiO layer. Again, three different deposition techniques of NiO were used and results were compared to organic p-type layers. The measured IV curves were compared to a drift-diffusion model for charge carriers, which gives insight into the solar cells operating mechanism.
Our study gives a detailed account of organic and inorganic blocking layer fabrication methods and their influence on the operational mechanism of perovskite solar cells. We hope that these findings help in the production of more efficient cells and aid a better understanding of the physics at the blocking layer-perovskite interface.
[360] PERFORMANCE OF SILICON NEGATIVE ELECTRODES WITH CNTS IN LI-ION SYSTEMS
Sivan Okashy1
1 Bar Ilan Univesity; Bar Ilan Univesity
Performance of silicon negative electrodes with CNTs in Li-ion systems
Sivan Okashy, Shalom Luski and Doron Aurbach
Department of chemistry, Bar Ilan University. Ramat-Gan 52900 Israel.
Silicon is capable of delivering a high theoretical specific capacity of 4200 mAh g-1 order of magnitude higher than that of the state-of-the-art graphite based negative electrodes for lithium-ion batteries. Using silicon- containing negative electrodes can increase significantly the energy density of the Li – -ion cell. However, the poor cycle life of silicon electrodes, caused by the large volumetric strain during cycling, limits the commercialization of silicon electrodes. As one of the essential components, the polymeric binder is critical to the performance and durability of lithium-ion batteries as it keeps the integrity of electrodes, maintains conductive path and must be stable in the electrolyte. When addressing micrometric Silicon the conductivity must be taken under consideration and can be compensated by conductive additives such as CNTs. In this work, we demonstrate that electrodes consisting of silicon micrometric mixed with commercially available sodium alginate as well as CNTs are able to maintain a high specific capacity over 1500 mAh g-1 150 cycled between 0.7 V and 0.05 V.
[369] INFLUENCE OF TIO2 PHOTOELECTRODE STRUCTURE IN QUANTUM DOT SOLAR CELLS PERFORMANCE
Lida Givalou1, Maria Antoniadou1, Maria Giannouri1, Athanassios Kontos1, Polycarpos Falaras1
1 National Center for Scientific Research Demokritos; Institute of Nanoscience and Nanotechnology
Influence of TiO2 Photoelectrode Structure in Quantum Dot Solar Cells Performance
Lida Givalou, Maria Antoniadou, Maria Giannouri, Athanassios G. Kontos, Polycarpos Falaras*
Institute of Nanoscience & Nanotechnology, NCSR Demokritos, 15310 Agia Paraskevi, Attiki, Greece
* Corresponding author: [email protected]
Quantum dots are used as low cost photosensitizers in order to replace the organic dyes and the transition metal complexes in dye sensitized solar cells. The main advantages of using quantum dots lay on the ability to tune the bandgap according to their particle size and the high molar extinction coefficients of the materials which permit the generation of high photocurrent density values. This particular behavior is due to its small particle size which is comparable to the de Broglie wavelength of the nanocrystalline semiconductor electrons. In this context, the use of quantum dots as photosensitizers, contributes to the preparation of efficient solar cells, which are known as Quantum Dot Sensitized Solar Cells (QDSSCs).
In this work, core/shell CdS-ZnS/CdSe QDs have been employed to assemble QDSSCs. The TiO2 photoanode structure has been optimized using several treatments including TiCl4, sol-gel compact layer, transparent layer and scattering layer approaches. The influence of the TiO2 film thickness on the cell performance has been examined as well. In addition, the porosity of the transparent layer has been controlled by modifying the ethyl cellulose concentration in the paste. The experimental results show that TiCl4 treatment increases the Jsc values but does not particularly improve the cell performance. Sol-gel works marginally better than TiCl4 as compact layer. The thickness increase for both the mesoporous film and the scattering layer improves the cell performance. Following a careful control on the balance between the scattering and mesoporous layer, the optimized CdSe /CdS-ZnS/ TiO2 QDSSCs demonstrated energy conversion efficiency (η) as high as 6.50% under one sun illumination (AM 1.5G, 100 mW cm− 2), which is among the highest values reported in the literature.
[388] CONTROLLING THE REACTIVITY OF ANATASE “CORES” USING COVALENTLY ATTACHED REDOX-ACTIVE INORGANIC PROTECTING LIGANDS
Manoj Raula1, Gal Gan Or2, Marina Sa2, Ira Weinstock2
1 Department of Chemistry and ; Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of Negev, Israel
2 Ilse Katz Institute for Nanoscale Science & Technology; Ben-Gurion University of Negev
Controlling the reactivity of anatase “cores” using covalently attached redox-active inorganic protecting ligands
Manoj Raula, Gal Gan-Or, Marina Saganovich and Ira A. Weinstock
Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of Negev, Israel
An unprecedented role for metal-oxide cluster-anions (polyoxometalates, or POMs) as covalently coordinated inorganic ligands for individual anatase nanocrystals, giving isolable anionic clusters uniquely positioned between molecular macroanions and traditional colloidal nanoparticles. Water-soluble polyanionic structures are obtained by reacting amorphous TiO2(s) with the 1-nm size mono-defect Keggin ion, Na(8-n)[α-Xn+W11O39], Xn+ = P5+, at 170 C, after which, an average of 55 ± 10 α-PW11O397- anions are found as pentadentate “capping” ligands for complexed Ti(IV) ions still linked—via their sixth coordination site—to 6-nm single-crystal anatase-TiO2 cores. Multiple lines of evidence reveal that the POM-protecting ligands are covalently bound to the surface of anatase nanocrystals, giving clear solutions over a wide range of pH values, and allowing for repeated precipitated and re-dissolution in water. EDS and XPS data suggest that numerous POMs are associated with each 6-nm anatase nanocrystal, and high-resolution TEM, cryogenic-TEM, and HAADF-STEM images clearly show POM-protecting ligands bound to anatase surfaces. Solid-state NMR and ESI-MS mass spectra unambiguously identify the covalently bound POM-protecting ligands as TiPW11O405–derived clusters. The surface-bound cluster-anions are reversible electron acceptors, whose reduction potentials shift to more negative values by simply changing the central heteroatom, Xn+, from P5+ to Si4+ to Al3+. Hence, just as POM cluster-anions control the reactivities of metal centers in molecular complexes, directly coordinated POM ligands with tunable redox potentials provide better control over the reactivity of TiO2 nanocrystal cores. This rational tuning of metal-oxide nanocrystal reactivity is demonstrated using photochemical hydrogen evolution from water.1
(1) Manoj Raula, Gal Gan Or, Marina Saganovich, Offer Zeiri, Yifeng Wang, Michele R. Chierotti, Roberto Gobetto, and Ira A. Weinstock, Angew. Chem. Int. Ed., 2015, 54, 12416-12421.(Highlighted as a Hot Paper)
[393] A NOVEL MESO/PLANAR HYBRID ARCHITECTURE OF METHYLAMMONIUM LEAD IODIDE BASED PEROVSKITE SOLAR CELLS
Ravi K Misra1, Bat-El Cohen2, Michael Layani3, Shlomo Magdassi4, Lioz Etgar5
1 Hebrew University of Jerusalem, Israel; Hebrew University of Jerusalem, Israel
2 The Hebrew University of Jerusalem; The Hebrew University of Jerusalem
3 Casali Institute for Applied Chemistry; Institute of Chemistry
4 Casali Center of Applied Chemistry; The Hebrew University of Jerusalem
5 Casali Institute of Applied Chemistry, Hebrew University of Jerusalem; Hebrew University of Jerusalem, Israel
A novel meso/planar hybrid architecture of methylammonium lead iodide based perovskite solar cells
Ravi K. Misra, Bat-El Cohen, Michael Layani, Shlomo Magdassi & Lioz Etgar
Casali Center for Applied Chemistry, Hebrew University of Jerusalem, Givat Ram Campus, Jerusalem, Israel-91904
Perovskite based solar cells have seen tremendous development in last five years and recently achieved a record efficiency of 20.1 %1. The high efficiency cells from the group usually based on meso-TiO2 as a base layer for perovskite infiltration, though the exact role of TiO2 in these cells is yet to be explained.
Here we are reporting for the first time a novel architecture of perovskite based solar cells, which, we prefer to call meso/planar hybrid architecture of perovskite solar cells. The deposition of meso-TiO2 after compact TiO2 blocking layer, has been done with the help of a grid in these cells similar to already reported by our group for the development of semitransparent solar cells2, followed by methyl ammonium lead iodide perovskite deposition using two step deposition process.
The initial results found promising with power conversion efficiency (PCE) of 7.9% with high open circuit voltage and reasonable current density of about 14 mA/cm2. The cells are supposed to be a good architecture to study the effect of interfaces on the cell performance using Impedance spectroscopy, since they have the compact-TiO2/perovskite (planar) interface on one hand, meso-TiO2/perovskite (meso) interface on the other hand. The detailed studies of this novel architecture, including their photovoltaic performance and effect of structural modifications on the cells PV properties will be the part of presentation.
Keywords: meso/planar hybrid architecture, perovskite solar cells, TiO2 grid, Methylammonium lead iodide perovskite
References:
1. http://www.nrel.gov/ncpv/images/effi ciency_chart.jpg. Accessed: March 2015.
2. Sigalit Aharon , Michael Layani , Bat-El Cohen , Efrat Shukrun , Shlomo Magdassi and Lioz Etgar, Self-Assembly of Perovskite for Fabrication of Semitransparent Perovskite Solar Cells, Adv. Mater. Interfaces 2015, 1500118.
[409] GA MODIFIED ZEOLITE BASED SOLID ACID CATALYST FOR LEVULENIC ACID PRODUCTION
Vijay Bhooshan Kumar1
1 Bar Ilan Institute for Nanotechnology and Advanced Materials; Bina, Department of Chemistry, Bar Ilan University
Ga modified zeolite based solid acid catalyst for levulenic acid production
Vijay Bhooshan Kumara, Indra Neel Pulidindia, and Aharon Gedankena, b*
aDepartment of Chemistry and Bar-Ilan Institute for Nanotechnology & Advanced Materials, Bar Ilan University, Ramat-Gan 52900, Israel
bNational Cheng Kung University, Department of Materials Science & Engineering, Tainan 70101, Taiwan
*Corresponding author email: [email protected]
Fax: 972-3-7384053; Tel: 972-3-5318315
ABSTRACT:
Gallium modified zeolite (mordenite) solid acid catalyst using the sonochemical method. The catalyst (Ga@Zeolite) was characterized using XRD, SEM, TEM, EDS, FTIR, DSC, and TGA analysis. It was found that Ga was inserted in the pores of zeolites. In addition, small Ga particles (5-60 nm) were found in between the zeolite crystals. The catalyst was further used for the production of levulinic acid from carbohydrates (glucose, molassa, sucrose, starch, and cellulose) in a hydrothermal process. Reaction conditions (time, ratio of amount of substrate and catalyst) for the optimum yield of levulinic acid were deduced (175 ˚C and 6 h). The reaction products were analysed qualitatively using NMR (1H and 13C) and quantitatively by HPLC analysis. The maximum yield of levulinic acid obtained from glucose was 60.4 wt. % and efficiency conversion is > 90%..
Keywords: Zeolite, Ga@mordenite, Hydrolysis, Hydrothermal process; Glucose; Levulenic acid
[412] HARSH REVERSE BIAS STRESS OF DYE SENSITIZED SOLAR CELLS MONITORED VIA ELECTRICAL AND SPECTROSCOPIC METHODS
Harry Georgiou1, Athanassios Kontos2, Antonio Agresti3, Aldo Di Carlo4, Sara Pescetelli5, Polycarpos Falaras2
1 National Centre for Scientific Research Demokritos; Agia Paraskevi
2 National Center for Scientific Research Demokritos; Institute of Nanoscience and Nanotechnology
3 Center for Hybrid and Organic Solar Energy; Chose
4 Dipartimento DI Ingegneria Elettronica and Chose; Tor Vergata
5 Tor Vergata; Center for Hybrid and Organic Solar Energy
HARSH REVERSE BIAS STRESS OF DYE SENSITIZED SOLAR CELLS MONITORED VIA ELECTRICAL AND SPECTROSCOPIC METHODS
Harry Georgioua, Athanassios G. Kontosa, Antonio Agrestib, Sara Pescetellib, Aldo Di Carlob and Polycarpos Falarasa
a Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 15310 Athens, Greece
b C.H.O.S.E. (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome Tor Vergata, via del Politecnico 1, 00133 Rome, Italy
Abstract
Harsh reverse bias has been applied in dye sensitized solar cells (DSCs) forcing a fixed short-circuit current of 250 mA for a duration of 165 hours. This test simulates real stress of shadowed DSCs and results in considerable degradation, about 30%, loss of their solar to electrical conversion efficiency. The degradation of the cells has been characterized by Linear Sweep Voltammetry, UV-VIS absorption spectroscopy and resonant Raman scattering diagnostics. The ageing of the DSCs resulted in increased luminescence background signals and significant changes in the Raman peak intensities with respect to the reference TiO2 peak at 143 cm-1; thus the intensity of the 169 cm-1 mode due to dye-triioidide complexes increases while the corresponding intensities of the triiodide 110 cm-1 and the dye 1543 cm-1 modes decrease. Reduction of the diffusion limiting currents and changes in the transmittance and reflectance signals indicate triiodide losses and justifies decrease of the fill factor, as the main reason for the reduction in efficiency of the DSCs. Curiously, at low irradiation level (0.1 sun) the cells present increased photocurrents and efficiencies after RB stress justified by the increase of the light absorbance by the dye due to the triiodide decrease while, at such low light intensities, the increase of the diffusion resistance has not any decisive role in the operation of the cells.
[413] CORE/SHELL SI-NI/C ANODES FOR HIGH-ENERGY-DENSITY LI-ION BATTERIES
Keren Goldshtein1, Meital Goor1, Kathrin Freeedman2, dan Schneier2, Diana Golodnitsky3, Emanuel Peled2
1 Tel-Aviv University; Tel-Aviv University
2 School of Chemistry; School of Chemistry
3 Honeycomb Batteries Ltd; Tel Aviv University
Core/Shell Si-Ni/C Anodes for High-Energy-Density Li-Ion Batteries
K. Goldshtein1, M. Goor1, K. Freedman1, Dan Schneier1, D. Golodnitsky1,2, and E. Peled1
1 – School of Chemistry; 2 – Wolfson Applied Materials Research Center,
Tel Aviv University, Tel Aviv, 69978
The goal of this research was the development of low-cost, high-capacity, long-cycle-life and safer anode materials to replace the graphite anode of the common lithium-ion battery. Silicon offers the highest gravimetric capacity as an anode material (e.g. Li22Si5: nearly 4,200mAh/g). However, Si-based electrodes typically suffer from large volume changes (up to 420%) during insertion and extraction of lithium. This is followed by cracking and pulverization of silicon, which in turn, leads to the loss of electrical contact, an unstable SEI and eventual capacity fading.
Our strategy for reducing the deterioration of silicon involve attaching silicon and silicon-nickel nanoparticles to multiwall carbon nanotubes (MWCNT) in order to create a silicon-based active anode material supported by a strong, rigid and high-electrically-conducting network. The method is based on the pyrolysis of the mixture of nanoparticles and nanotubes with carbon precursor. Silicon-nickel alloying is achieved by electroless or grinding process followed by pyrolysis. Nickel was chosen since, when alloyed with silicon, this metal is expected to stabilize the structure of lithiated silicon nanoparticles, increase electron conductivity and possibly induce graphitization of the carbon shell.
Li/SiNi-MWCNT-C (1.6mg/cm2 loading) cells exhibited a de-intercalation capacity of 900mAh/ganode at C/7, 600mAh/ganode at C/3.4 and 400mAh/ganode at C/1.7. Irreversible capacity of 22% and high faradaic efficiency (FE) of 99.5% were obtained. Very highly loaded anodes, weighing 5.5mg/cm2, with de-intercalation capacities of 1000mAh/ganode, demonstrated stable cycle life three times greater than that of graphite.
[488] ELECTROCHEMICAL REDUCTION OF CARBON DIOXIDE USING CATALYTIC PORPHYRIN/GRAPHENE SYSTEMS
Yair Bochlin1
1 Iki; Ben Gurion University
Electrochemical Reduction of Carbon Dioxide Using Catalytic Porphyrin/Graphene Systems
Yair Bochlin, Eli Korin and Armand Bettelheim
Department of Chemical Engineering, Ben-Gurion University of the Negev
P.O.B. 653, Beer Sheva 8410501
[email protected]
The CO2 levels in air have been increasing over the past few decades. The conversion of CO2 back to fuels is a critical goal that would restore balance to the rising CO2 levels. CO2 is a very stable, linear molecule, and returning it to a useful state in the form of fuels is a challenging problem. CO2 reduction is possible through chemical catalysis, electrochemistry, photo-chemistry and biological processes. Chemical catalytic processes generally operate at high temperatures and pressures which lead to high energy cost.
The electrocatalytic capabilities toward CO2 reduction of some cobalt porphyrins have been reported. The present work deals with the spectroscopic and electrochemical examination of the interactions occurring between such porphyrins and graphene derivatives, and their effect on CO2 reduction. Such self-assembled systems formed between 5,10,15,20-Tetrakis(1-methyl-4-pyridinio) porphyrin (CoTMPyP) and graphene carboxyl were deposited on electrode surfaces (such as glassy carbon) by means of adsorption or electrodeposition.
The electrodeposited system showed increased activity for CO2 reduction compared to an inert environment (1.2 mA/cm2 and 0.25 mA/cm2, respectively, at -1.2V vs. Ag/AgCl) as examined in an aqueous 0.1 M Na2CO3 solution at pH 11.5.
[491] NANOHETEROSTRUCTURE PHOTOCATALYST DESIGN
Sandip Pahari1, Lilac Amirav2
1 Israel Institute of Technology, Technion; Schulich Faculty of Chemistry
2 Schulich Faculty of Chemistry; Technion – Israel Institute of Technology
Nanoheterostructure Photocatalyst Design
Sandip Kumar Pahari, Lilac Amirav
Schulich Faculty of Chemistry, Technion – Israel Institute of Technology
Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology
Haifa, 3200008, Israel, Tel: +972-4-829-3715. E-mail: [email protected]
Abstract:
The solar-driven photocatalytic splitting of water into hydrogen and oxygen is a potential source of clean and renewable fuel. Solar-to-fuel energy conversion alleviates the energy storage problem, since fuel can be stored more easily than either electricity or heat. After four decades of global research systems that are sufficiently stable and efficient for practical use have not yet been realized.
The photocatalyst activity is strongly correlated with its structure, morphology and composition. Hence, the design of effective artificial photocatalytic systems depends on our ability to precisely control these parameters. Here we present the design and synthesis of advanced photocatalysts, based on innovative nano scale hybrid particles. Our multi-component nanoheterostructure combines semiconductors (CdSe@CdS) with metal (e.g. Pt and Ni) and metal oxide (e.g. Fe2O3) co-catalysts, in a controlled and variable spatial arrangement. Our design targets improved charge separation, facilitates formation of distinct redox reaction sites, and minimize back reaction of intermediates. In particular we examine utilization of hollow structures for the oxidation half reaction in order to facilitate close proximity of intermediates and assist the forward reaction in this complex multi-step process.
[492] ANISOTROPIC PLASMONIC METAL-SEMICONDUCTOR NANOHYBRIDS
Firdoz Shaik1, Imanuel Peer2, Lilac Amirav3
1 Russell Berrie Nanotechnology Institute; Technion-Israel Institute of Technoloy
2 Russell Berrie Nanotechnology Institute; Technion – Israel Institute of Technology
3 Schulich Faculty of Chemistry; Technion – Israel Institute of Technology
Anisotropic Plasmonic Metal-Semiconductor Nanohybrids
Firdoz Shaik, Imanuel Peer and Lilac Amirav
Schulich Faculty of Chemistry, Technion – Israel Institute of Technology
Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology
Haifa, 3200008, Israel, Tel: +972-4-829-3715. E-mail: [email protected]
Plasmonic nanostructures are known to enhance by orders of magnitude various light-matter interactions. The use of plasmon resonances to manipulate optical processes in semiconductors has been gaining increasing attention. Here we present a synthesis of controlled plasmonic nanostructure/quantum dot (QD) dimers, optimized for maximal field enhancement. We are particularly interested in anisotropic plasmonic metal nanoparticles that exhibit unique optical and electrical properties as compared to spherical plasmonic metal nanoparticles. These heterostructures will serve as model systems for exploring and exploiting plasmon-enhanced photophysical processes.
We report here on the synthesis of Au nanoprism@SiO2@CdSe-QDs nanohybrids. Au nanoprisms were synthesized by using a one-pot seedless method through oxidative etching process. The silica shell, which was deposited on the Au nanoprisms by a sol-gel method, was functionalized with amine groups to which CdSe QDs were connected. The distance between CdSe QDs and Au nanoprisms can be controlled by fine-tuning the thickness of the silica shell. This synthetic strategy can be extended for the synthesis of other complex anisotropic plasmonic metal-semiconductor nanohybrids. We believe these plasmonic/QD nanohybrids can become generalized systems for studying and discovering a range of nano-optic phenomena, and serve as groundwork for the development of several important applications, such as improved solar energy harvesting systems.
[505] GRAPHITE/CARBON BLACK NANOCOMPOSITE COUNTER ELECTRODE FOR PEROVSKITE SOLAR CELLS
surendra kumar yadav1
1 C.H.O.S.E. (Centre for Hybrid and Organic Solar Energy), Department of Electronics Engineering; Via Polytecnico 1
Graphite/Carbon black nanocomposite counter electrode for perovskite solar cells
Surendra K. Yadav1, , Francisco Fabregat Santiago2, Eva M. Barea2, , Fabio Matteocci1, Juan Bisquert2, Aldo Di Carlo1
1C.H.O.S.E. (Centre for Hybrid and Organic Solar Energy), Department of Electronic Engineering, University of Rome “Tor Vergata”,via del Politecnico 1, Rome, 00133 Italy.
2Photovoltaics and Optoelectronic Devices Group, Departament de Fisica, Universitat Jaume I, 12071 Castello, Spain.
Email: [email protected]
Recently, methylammonium lead halide have invoked remarkable amount of scientific and commercial attention for developing cost-effective, high-efficiency solar cells to meet the ever increasing demand for clean energy. Hole conductors such as the widely used Spiro-OMeTAD is not only expensive but can limit the long-term stability of the device. Carbon derivatives are of great interest as counter electrode material in hole−conductor free TiO2/(ZrO2 or Al2O3)/perovskite/Carbon derivative heterojunction solar cells to substitute noble metallic materials. The hydrophobic and porous carbon derivatives could be the possible solution for high performance cost effective and long term stable Perovskite solar cells (PSCs). To characterize the perovskite- carbon interface, we considered an equivalent electrochemical cell contains Iodide/Tri-iodide redox couple instead of Perovskite. This system has similar energetics as the carbon/perovskite and, at the same time, is more stable. We fabricate Graphite/carbon film of different thickness and follow many procedures to make it stable. The graphite/carbon black nanocomposite film characterised by impedance spectroscopy, transport resistance and double layer capacitance of various carbon films shows that the charge transport is faster in sample 1. The optimum thickness for significant charge transfer is (10µm-14µm) and slow ramp for sintering have added advantage for better stability of nanocomposite film.
Figure1: Transport resistance and double layer capacitance of various types of nanocomposite film specimens.
References:
1. Anyi Mei, Min Hu, Xiong Li, Linfeng Liu, Jiangzhao Chen, Ying Yang, Zhiliang Ku, Tongfa Liu, Michael Grätzel, Yaoguang Rong, Hongwei Han, Science, 345,6194, (2014).
[534] THE EFFECT OF PT:RU RATIO ON THE ACTIVITY OF CORE-SHELL METHANOL OXIDATION CATALYSTS
Dima Kaplan1, Larisa Burstein1, Yuri Rosenberg1, Inna Popov2, Emanuel Peled3
1 School of Chemistry; Wolfson Applied Materials Research Center
2 School of Chemistry; The Hebrew University Center for Nanoscience and Nanotechnology
3 School of Chemistry; School of Chemistry
The effect of Pt:Ru ratio on the activity of Core-Shell methanol oxidation catalysts
D. Kaplan*, L. Burstein**, Yu. Rosenberg**, I Popov***, and E. Peled*
*School of Chemistry, **Wolfson Applied Materials Research Center
Tel Aviv University, Tel Aviv, Israel, 69978
***The Hebrew University Center for Nanoscience and Nanotechnology
The Hebrew University of Jerusalem, Jerusalem 91904, Israel
Presenting author contact information: [email protected], 03-6406951
Direct methanol fuel cells (DMFCs), using liquid and renewable methanol fuel, have been considered to be a favorable option in terms of fuel usage and feed strategies. However, in order to make DMFC technology a success, real breakthroughs in anode catalysis are necessary with respect to performance and cost. Regarding cost reduction, for early DMFC commercialization, DMFC anode catalyst loadings must drop to a level of <1.0 mg cm−2 from the present 1.0–8.0 mg cm−2.
The purpose of our research was to develop catalysts with high platinum utilization, and also to study the correlation between the surface concentrations of platinum and ruthenium and the methanol oxidation activity. Core – Shell catalysts have the potential to improve Pt utilization and reduce the currently needed Pt loadings in DMFC. Several nano-size (2-3nm) Core – Shell, XC72 supported catalysts were synthesized in a two-step successive deposition process with NaBH4 as the reducing agent. The catalysts were composed of IrNi core and varying Pt:Ru ratio shell, from Pt:Ru=0.3 to Pt:Ru=4. The structure and composition of these core-shell catalysts were determined by EDS, XPS, TEM and XRD. Electrochemical characterization was determined with the use of cyclic voltammetry. The methanol oxidation activities of the Core – Shell catalysts were studied at 80°C and compared to that of the best commercially available PtRu alloy based catalyst. A 48% improvement of catalytic activity (in terms of A g-1 of platinum) over the commercial catalyst was achieved. These results demonstrate the potential of Core – Shell catalysts in reducing the costs of catalysts for DMFC.