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Two new random donor-acceptor (D-A) copolymers, signed as P1 and P2, were designed and synthesized. Electrochemical and spectroelectrochemical measurements were performed to investigate absorption, energy levels, electronic and optical band gaps for comparison. The polymers were used as donor polymers in the active layer to fabricate non-fullerene, bulk heterojunction (BHJ) organic photovoltaics (OPVs). Investigations were carried out through the conventional BHJ structure; ITO/PEDOT: PSS/Active Layer/LiF/Al, where active layer consists of 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) as the acceptor and thienopyrroledione containing donors. The device based on P1:ITIC(1:1) blend with a thickness of 161 nm gave the best performance with a power conversion efficiency (PCE) of 7.94%, an open-circuit voltage (V-OC) of 0.86 V, a short-current density (J(SC)) of 18.45 mA cm(-2) and a fill factor (FF) of 50.12%. The highest PCE obtained from P2 based organic solar cell is 1.96%. P2 exhibited low solubility attributed to the lack of alkyl groups enhancing polymer solubility, electronic properties, and photovoltaic performances. The research outputs exhibit that introduction of alkyl chains on the polymer backbone can enhance device performance. (C) 2021 Elsevier Ltd. All rights reserved.

This study details the development of a solid-state complementary metal-oxide semi-conductor (CMOS)-compatible glucose fuel cell, consisting of various amounts (% wt.) carbon nanohorns (CNHs). It was fabricated on an anode area using one-dimensional (1D) structural CNHs, which express an open-circuit voltage (OCV) of 375 mV, the power density of 8.64 µW/cm2 and current density 23.05 µA/cm2 in 30 mM glucose solution. The cell can be manufactured via a CMOS fabrication process, using materials biocompatible with the human body. The CNHs enhanced the fuel cell due to their high electrocatalytic ability. Here, CNHs were used to fabricate a 17.5 mm × 0.7 mm solid-state CMOS-compatible glucose fuel cell with 375 mV of OCV - the highest reported value for such a cell with an anode area of 16.2 mm × 0.3 mm. The highest power is 0.42 µW. Power generation is the main challenge for developing glucose fuel cells to make the implantable devices that can be used for biomedical applications.

Direct Alcohol Fuel Cell (DAFC) performance is influenced by electrocatalysis reactions that occur in Membrane Electrode Assembly (MEA). In this study, MEA was made with Pt-Ru/C (anode) and Pt/C (cathode) catalysts. The results of the electrode characterization with XRD showed a carbon peak at 26.63° and Ru at 40.58°. Based on the results of Cyclic Voltammetry (CV) measurements, the Electrochemical Surface Area (ECSA) electrode value is known to be 373.601 cm2/mg. Meanwhile, the impedance value is 4.315 Ω and the electrical conductivity value is 6.61x10-4 S/cm. MEA testing using MeOH 3 M fuel produces Open Circuit Voltage (OCV) of 0.650 V. Meanwhile, MEA performance testing uses a mixture of methanol and ethanol 2 M in loading conditions obtained the best mixture of fuel composition is methanol: ethanol = 90:10 with a maximum power density of 4.34 mW/cm2 and is able to maintain the voltage at 0.649 V under conditions of 6.875 mA/cm2. The results also showed that the volume of ethanol which was too high resulted in a decrease in cell performance in the fuel mixture caused by the competition of adsorption between competing methanol and ethanol occupying the active site of the catalyst. Keywords: DAFC, fuel cell, Pt-Ru/C, ethanol, methanol, Open Circuit Voltage

By using electrical characterization and classical solid state semiconductor device theory, we demonstrate that the open circuit voltage (Voc) in organic solar cells based on non-intentional doped semiconductors is fundamentally limited by the built-in potential (Vbi) originated at a donor-acceptor abrupt (p-n++) heterojunction in case of selective contacts. Our analysis is validated using P3HT:PCBM devices fabricated in our research group. We also demonstrate that such a result can be generalized using data already reported in literature for fullerene-based solar cells. Finally, we show that the dependence of Voc on the device contacts can be understood in terms of the potential barriers formed by the Fermi level alignment of semiconductors at the heterojunction and at the Schottky junctions.

International audience; Engineering the surface at the rear interface between the perovskite and the hole transporting material is of paramount importance to minimize nonradiative losses. We report the use of N-bromosuccinimide (NBS), as an interfacial alleviator to influence crystallization of the perovskite and defect passivation. The NBS treatment promotes enhanced charge extraction and improved photovoltaic performance. Thus, formed perovskite layers exhibit grain size increments and lowered trap density. An improved device performance was noted with an optimized concentration of 0.5% NBS as compared to pristine perovskite due to the increment in open circuit voltage and short circuit current density. The coordination of bromide influences the crystal lattice as shown by polarization-modulated-infrared reflection−absorption spectroscopy, which in turn may influence charge transport and interfacial properties.

Green sensors are required for the realization of a sustainable economy. Biopolymer-derived composites are a meaningful solution to such a needing. Bacterial Cellulose (BC) is a green biopolymer, with significant mechanical and electrical properties. BC-based composites have been proposed to realize generating mechanoelectrical transductors. The transductors consist of a sheet of BC, impregnated of Ionic Liquids (ILs), and covered with two layers of Conducting Polymer (CP) as the electrodes. Charges accumulate at the electrodes when the transductor is bent. Generating sensors can produce either Open Circuit (OC) voltage or Short Circuit (SC) current. In the paper, the OC voltage and SC current, generated from BC-based composites, in a cantilever configuration and subjected to dynamic deformation are compared. The influence of ILs in the transduction performance, both in the case of OC voltage and SC current is investigated. Experimental investigations of structural, chemical, and mechanoelectrical transduction properties, when the composite is dynamically bent, are performed. The mechanoelectrical investigation has been carried on both in the time and in the frequency domains. Reported results show that no relevant changes can be obtained because of the use of IL when the OC voltage is considered. On the contrary, dramatic changes are observed for the case of SC current, whose value increases by about two orders of magnitude.

The performances of Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) anode-supported planar cells with a 10 cm2 active surface were studied versus the combination of cathode thickness and the presence of an Anode Functional Layer (AFL). The temperature range was 500 to 650 °C, and Gd0.1Ce0.9O2−x (GDC) was used as the electrolyte material, Ni-GDC as the anode material, and La0.6Sr0.4Co0.2Fe0.8O3−d (LSCF48) as the cathode material. The power density, conductivity, and activation energy of different samples were determined in order to investigate the influence of the cathode thickness and AFL on the performance. These results showed an improvement in the performances when the AFL was not present. The maximum power density reached 370 mW.cm−2 at 650 °C for a sample with a cathode thickness of 50 µm and an electrolyte layer that was 20 µm thick. Moreover, it was highlighted that a thinner cathode layer reduced the power density of the cell.

Mixed-cation and halide perovskite solar cells have shown superior photovoltaic performance compared to mono-cation based representatives. Their remarkable photovoltaic performance is the effect of superior compositional engineering along with their unique optoelectronic properties. However, there is still a lack of understanding of the working principles of multi-cation based perovskite solar cells. In this study, we employ the state-of-the-art multiple-cation perovskites FA0.83MA0.17Pb(I0.83Br0.17)3 and Cs5(MA0.17FA0.83)95Pb(I0.83Br0.17)3 as absorber layers and investigate their intrinsic and interfacial dynamics in planar TiO2-based PSCs. We demonstrate that the incorporation of Cs+ in FA0.83MA0.17Pb(I0.83Br0.17)3 leads to an increase in power conversion efficiency, improved perovskite phase stability and reduced recombination. However, these devices along with these excellent characteristics still suffer from lower open circuit voltage (Voc) as compared to FA0.83MA0.17Pb(I0.83Br0.17)3 based devices. By analysing the morphological properties and capacitance versus frequency responses, we show that the higher grain size and higher accumulation of photogenerated charges lead to the high open circuit voltage in FA0.83MA0.17Pb(I0.83Br0.17)3 based devices. Our results demonstrate that the values of Voc not only depend on the recombination, but also on charge accumulation phenomena. Accepted version D. P. acknowledges the financial support from the HOMING programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund (POIR.04.04.00-00-5EE7/18-00). M. M. T., and P. Y. want to thank the laboratory of photonics and interfaces (LPI) at Ecole Polytechnique Fe´de´rale de Lausanne (EPFL).

Dual junction tandem solar cells can utilize from the solar spectrum photons with broader range of energies as compared to the conventional single junction solar cells thereby demonstrating higher conversion efficiency. This paper deals with the numerical modeling of a dual junction GaInP/Si based multijunction tandem photovoltaic cell. The semi empirical modeling approach was used for simulation which produced a theoretical one sun conversion efficiency of over 30% for the proposed four terminal configuration.

In this work, we present an extensive characterization of plasma-assisted atomic-layer-deposited SnO2 layers, with the aim of identifying key material properties of SnO2 to serve as an efficient electron transport layer in perovskite solar cells (PSCs). Electrically resistive SnO2 films are fabricated at 50 °C, while a SnO2 film with a low electrical resistivity of 1.8 × 10-3 ω cm, a carrier density of 9.6 × 1019 cm-3, and a high mobility of 36.0 cm2/V s is deposited at 200 °C. Ultraviolet photoelectron spectroscopy indicates a conduction band offset of ∼0.69 eV at the 50 °C SnO2/Cs0.05(MA0.17FA0.83)0.95Pb(I2.7Br0.3) interface. In contrast, a negligible conduction band offset is found between the 200 °C SnO2 and the perovskite. Surprisingly, comparable initial power conversion efficiencies (PCEs) of 17.5 and 17.8% are demonstrated for the champion cells using 15 nm thick SnO2 deposited at 50 and 200 °C, respectively. The latter gains in fill factor but loses in open-circuit voltage. Markedly, PSCs using the 200 °C compact SnO2 retain their initial performance at the maximum power point over 16 h under continuous one-sun illumination in inert atmosphere. Instead, the cell with the 50 °C SnO2 shows a decrease in PCE of approximately 50%. © 2018 American Chemical Society.

The composite of samarium doped ceria (Sm0.2Ce0.8O2-delta, SDC) and co-doped barium cerate (BaZr0.1Ce0.7Y0.1Yb0.1O3-delta, BZCYYb) is prepared by mechanical mixing and investigated as electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). Coexistence of SDC and BZCYYb are observed for composite electrolyte by X-ray diffraction after sintering at 1500 degrees C for 5 h, while the slight deviation of the diffraction peak indicating the element diffusion between two phases. The scanning electron microscope and electron probe microanalyzer results demonstrate that small BZCYYb grains disperse uniformly around the grains of SDC, limiting the growth of SDC grains and decreasing the average grain size of composite electrolyte. Impedance spectroscopy measurement reveals that the grain boundary resistance can be significantly reduced by about an order of magnitude through adding 15-30 wt. % BZCYYb to SDC. Single cells based on the composite electrolyte are fabricated using nickel cermet (Ni-SDC) anode and perovskite (La0.6Sr0.4Co0.2Fe0.8O3-delta, LSCF) cathode., Relatively high open circuit voltage (OCV), much lower polarization resistance and encouraging high power density are obtained for cells with composite electrolyte compared to those with single SDC electrolyte. Among all of the samples, single cell based on 15 wt. % BZCYYb-85 wt. % SDC composite electrolyte exhibits the lowest total resistances of 0.641 Omega.cm(2) and the highest peak power densities of 0.56 W. cm(-2) at 600 degrees C. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

We report on two differentapproaches to fabricateinterdigitated back contact silicon heterojunction solarcells without using indium tin oxide (ITO). The standard ITO/Ag backend is either modified by replacing ITO with aluminum-doped zinc oxide (AZO) or completely replaced by a sole aluminum (Al) layer. The very transparent AZO enhances the optical properties at the rear side resulting in an increase in short-circuit current density.The efficiency of the AZO cells remains on the level of the ITO ones, as the fillfactor drops slightly. On the contrary, the contact resistivity of annealed Al, in comparison to ITO and AZO, to the emitter and BSF layers is much lower, thus the fill factor is increased. Despite lower open circuit voltages,cells with Al achieve efficiencies of up 22 %, a gain of 0.5 %abs compared to the ITO reference.

WOS: 000524014100001, In this study, azobenzene and coumarin functionalized thiophene comprising two copolymers (poly (4-((3"'-hexyl-[2,2 ':5 ',2 '':5 '',2"'-tetrathiophene] - 3 '-yl)methoxy) - 2H-chromen-2-one (P1) and poly (1-(4-((4"'-hexyl-[2,2 ': 5 ', 2 '': 5 '', 2"' - tetrathiophene] - 3 '-yl) methoxy) phenyl) -2-phenyldiazene) (P2)), were designed and synthesized according to the donor-acceptor (D-A) approach to investigate their electrochemical, optical and photovoltaic behaviors. Among the various copolymerization methods to obtain P1 and P2, Stille copolymerization reaction was preferred. The HOMO and LUMO values were determined via cyclic voltammetry (CV) as -5.64 eV and -3.76 eV for P1 and -5.47 eV and -3.83 eV for P2, respectively. The optical band gaps of the polymers were calculated as 1.88 eV and 1.64 eV using UV-VIS spectrophotometer for P1 and P2. Electrochemical and spectroelectrochemical studies for synthesized copolymers support their usage in organic solar cell applications. The organic solar cells (OSCs) were designed using polymer as an electron donor group and PC60BM as an electron acceptor group. Performances of OSCs based on P1 and P2 were investigated with the device structure of ITO/PEDOT:PSS/Polymer(P1/P2):PC60BM/LiF/Al. The preliminary solar cell results were reported here and studies are going on in our laboratories to increase the efficiency. The highest power conversion efficiency was obtained as 0.81% for P1 based device with 0.47 V open-circuit voltage (V-oc) and 4.92 mA/cm(2) current density (J(sc)) values. The highest efficiency for P2 comprising device was found to be 0.96% under optimum conditions with 0.60 V and 4.98 mA/cm(2), V-oc and J(sc) values, respectively.

Segmented cells enable real time visualization of the flow distribution in vanadium redox flow batteries by local current or voltage mapping. The lateral flow of current within thick porous electrodes, however, impairs the local resolution of the detected signals. In this study, the open circuit voltage immediately after the cessation of charge/discharge is used for the mapping of reactant conversion. This quantity is not hampered by lateral flow of current and can be conveniently transformed to the corresponding state of charge. The difference between theoretically calculated and experimentally determined conversion (change in the state of charge) across the electrode is used to determine local variations in conversion efficiency. The method is validated by systematic experiments using electrodes with different modifications, varying current densities and flow configurations. The procedure and the interpretation are simple and scalable to any size of flow cell. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Published version

The open circuit voltage of lithium ion batteries in equilibrium state, as a vital thermodynamic characteristic parameter, is extensively studied for battery state estimation and management. However, the time-consuming relaxation process, usually for several hours or more, seriously hinders the widespread application of open circuit voltage. In this paper, a novel voltage relaxation model is proposed to predict the final open circuit voltage when the lithium ion batteries are in equilibrium state with a small amount of sample data in the first few minutes, based on the concentration polarization theory. The Nernst equation is introduced to describe the evolution of relaxation voltage. The accuracy and effectiveness of the model are verified using experimental data on lithium ion batteries with different kinds of electrodes (LiCoO2/mesocarbon-microbead and LiFePO4/graphite) under different working conditions. The validation results show that the presented model can fit the experimental results very well and the predicted values are quite accurate by taking only 5 min or less. The satisfying results suggest that the introduction of concentration polarization theory might provide researchers an alternative model form to establish voltage relaxation models.

In this work, impacts of temperature and dust cleaning on photovoltaic module performance operating in sub-Saharan's climate are investigated. Two single junction technologies, monocrystalline and polycrystalline silicon, and one micromorph (amorphous/micrystalline) thin film silicon tandem technology are considered. We have recorded at the same time under real operating conditions, the module temperature and the current versus voltage characteristics of each module, and the local solar irradiation. All the measurements were performed with the outdoor monitoring and test facility located at Ouagadougou in Burkina Faso. The results show the drop of generated power of dusty modules for the same irradiation level. Between April and June (where temperatures are higher) a significant drop of output power is observed, despite a daily cleaning. Furthermore, performance losses are observed for all technologies compared to that under standard test conditions. However, the micromorph silicon tandem technology with low temperature sensitivity present the less losses in performance compared to the monocrystalline and the polycrystalline single junction modules, even if the modules are not cleaned.

We have investigated the effect of thermal annealing on the photovoltaic parameters of all-polymer solar cells based on a quinoxaline-thiophene donor polymer (TQ1) and a naphthalene diimide acceptor polymer (N2200). The annealed devices show a doubled power conversion efficiency compared to nonannealed devices, due to the higher short-circuit current (J(sc)) and fill factor (FF), but with a lower open circuit voltage (V-oc). On the basis of the morphology-mobility examination by several scanning force microscopy techniques, and by grazing-incidence wide-angle X-ray scattering, we conclude that better charge transport is achieved by higher order and better interconnected networks of the bulk heterojunction in the annealed active layers. The annealing improves charge transport and extends the conjugation length of the polymers, which do help in charge generation and meanwhile reduce recombination. Photoluminescence, electroluminescence, and light intensity dependence measurements reveal how this morphological change affects charge generation and recombination. As a result, the J(sc) and FF are significantly improved. However, the smaller band gap and the higher HOMO level of TQ1 upon annealing causes a lower V-oc. The blend of an amorphous polymer TQ1, and a semi-crystalline polymer N2200, can thus be modified by thermal annealing to double the power conversion efficiency. Refereed/Peer-reviewed

In this work, organic photosensitizer has been synthesized for dye-sensitized solar cells (DSSCs). The solar cells then fabricated have been characterized by photocurrent-voltage characteristics and electrochemical impedance spectroscopic (EIS) measurements. The effect of outdoor temperature on the photovoltaic performance of DSSCs has also been investigated here. The results indicate that DSSC shows power conversion efficiency of 2.58% at 25 °C under air mass (AM) 1.5 G illumination at 100 mW/cm2. It has also been found out that the efficiency of DSSCs drops with the rise of temperature. The decrease in efficiency can be attributed to decrease in open-circuit voltage of cells. The EIS analysis shows that increase in temperature also reduces the charge recombination resistance mainly due to decrease of electron lifetime. These findings demonstrate that the cell is stable up to 35 °C. The authors acknowledge the support rendered by the CoRE-RE, KFUPM. Appendix A Scopus

International audience; We report on an improvement of the open circuit voltage over 0.8 V, together with decent fill factor and large short circuit current, through the incorporation of ester-functionalized single wall carbon nanotubes in a poly(3-hexylthiophene): 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61bulk heterojunction solar cell. The technique may open new margins for an extra efficiency enhancement through increase of the open circuit voltage using state of the art highly crystalline low band gap bulk heterojunction polymer solar cells.

Cupric oxide (CuO) is one of the most promising p-type semiconducting materials used in p-n junction solar cells. Most of the researchers use electrochemical deposition (ECD) to deposit CuO film. However, it always requires a conductive substrate and the resulting film is porous. In this work, we demonstrated a simple method using an immersion technique to deposit nanostructured CuO for p-n solar cell application. Compared to ECD which end up with only pyramid-like structure, an immersion technique offers flexibility on the CuO nanostructures such as spheres, particles, diamond etc. This technique also offers higher deposition rate which allow deposition at thicker thickness. The adherence to the substrate can be manipulated depending on the pH of the solution. The resulting film was tested into a p-n solar cell using configuration of Au/ZnO/Cuo/ITO/glass. Although there is no efficiency obtained under the solar radiation, it shows a solar cell characteristic with open circuit voltage (Voc) of 1.5V. We also found that without annealing, CuO is crystalline.

One of the key parameters in determining the power conversion efficiency (PCE) of bulk heterojunction (BHJ) organic solar cells (OSCs) is the open circuit voltage . The processes of exciting the donor and acceptor materials individually in a BHJ OSC are investigated and are found to produce two different expressions for . Using the contributions of electron and hole quasi-Fermi levels and charge carrier concentrations, the two different expressions are derived as functions of the energetics of the donor and acceptor materials and the photo-generated charge carrier concentrations, and calculated for a set of donor-acceptor blends. The simultaneous excitation of both the donor and acceptor materials is also considered and the corresponding , which is different from the above two, is derived. The calculated from the photoexcitation of the donor is found to be somewhat comparable with that obtained from the photoexcitation of the acceptor in most combinations of the donor and acceptor materials considered here. It is also found that the calculated from the simultaneous excitations of donor and acceptor in BHJ OSCs is also comparable with the other two . All three thus derived produce similar results and agree reasonably well with the measured values. All three depend linearly on the concentration of the photoexcited charge carriers and hence incident light intensity, which agrees with experimental results. The outcomes of this study are expected to help in finding materials that may produce higher and hence enhanced PCE in BHJ OSCs.

In this work, nickel thin films were deposited on texture silicon by electroless plated deposition. The electroless-deposited Ni layers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), and sheet resistance measurement. The results indicate that the dominant phase was Ni2Si and NiSi in samples annealed at 300–800 °C. Sheet resistance values were found to correlate well with the surface morphology obtained by SEM and the results of XRD diffraction. The Cu/Ni contact system was used to fabricate solar cells by using two different activating baths. The open circuit voltage (Voc) of the Cu/Ni samples, before and after annealing, was measured under air mass (AM) 1.5 conditions to determine solar cell properties. The results show that open circuit voltage of a solar cell can be enhanced when the activation solution incorporated hydrofluoric acid (HF). This is mainly attributed to the native silicon oxide layer that can be decreased and/or removed by HF with the corresponding reduction of series resistance.

Unlike the conventional solution processable deposition techniques, in this study, we propose a novel and economical method for the fabrication of organic rectifying junctions. The solutions of the orange dye, copper phthalocyanine and NaCl were deposited on the surface-type interdigitated silver electrodes using electrolysis technique. Using the current-voltage (I-V) characteristics, the presence of rectifying behavior in the samples has been confirmed. This phenomenon, in principle, can be used for fabrication of the diodes, transistors and memory devices. 1 2017, Springer-Verlag GmbH Germany. Scopus

In this study electricity generation was evaluated in a two chambered microbial fuel cell. Performance of microbial fuel cells using two bacteria, Klebsiella pneumoniae and Bacillus coagulans and using three different electrodes namely graphite blocks, carbon cloth and graphite sheet was studied. The device was operated under anaerobic condition in the anode chamber and parameters were recorded for a period of 48 hours. The performance of MFC was analyzed by the measurement of open circuit voltage, polarization curves, impedance curves and cyclic voltammetry. Among different combinations of electrode tested, carbon cloth electrode produced high power density (80 mW/m2). Graphite block gave much high power compared to sheet. Finally, performance was compared with Shewanellaputrefaciens. The current study explores the applicability of carbon electrode for MFC applications.

The photovoltaic properties of a good rectifying Al/ZnO/pSi/Al Schottky diode are studied. The diode was fabricated from two processes like ultrasonic spray pyrolysis @ 350°C for the ZnO layer on p-type Si substrate and thermal evaporation in vacuum at 10-6Torr for the metallic contacts. The current-voltage (I-V) measurements show a good rectifying behavior. Therefore, the extracted parameters are calculated in dark and illumination in one hand and under heating conditions in other hand. Ideality factor is lower around 1.5. Barrier height and series resistance, determined by Cheung-Cheung and Norde methods, are found to be 0.6-0.9 V and 1.4-5.4 kΩ. The parameters are influenced by increasing temperature; barrier height goes from 0.7 to 0.9 V and series resistance range within the range 1.2 -2.5 kΩ. Under light (150 W), the open circuit voltage and short circuit are found to be 0.09 V and 0.3 μA, the fill factor is of 0.44.Keywords: Schottky barrier diode; the sprayed ZnO film; Current-voltage characteristics; Good rectifying behavior; Open circuit voltage; Barrier height; Series resistance.

Reverse electrodialysis (RED) is one of the most promising membrane-based processes for renewable energy generation from mixing two solutions of different salinity. However, the presence of Mg2+ in natural water has been shown to drastically reduce open circuit voltage (OCV) and output power of RED. To alleviate this challenge, commercial cation exchange membranes (CEM) supplied by Fujifilm Manufacturing Europe B.V. (The Netherlands) were chemically modified by polypyrrole (PPy)/chitosan (CS) composites under controlled Pyrrole (Py) concentration (0.025–1 M) and polymerization time (0–8 h). The modified membranes were physically characterized by FTIR, SEM and EDX along with the determination of key electrochemical properties like ion exchange capacity, ionic conductivity, monovalent selectivity and swelling degree. The monovalent selectivity (Na+ vs Mg2+) of the modified membranes, evaluated based on flux of ions by diffusion dialysis, indicated up to 3-fold improvement compared to pristine membranes inline with the enhanced OCV (up to 20%) during RED test in multi-ion solution. This was obtained without significant change in membrane and interface resistances as depicted by electrochemical impedance spectroscopy. The modified membranes displayed power densities in the range of 0.6–1.5 W/m2MP (MP: membrane pair) with more than 42% improvement compared to pristine membranes during RED test with multi-ion solutions. Although there is a gap for further improvement, these findings highlight a promising use of conducting polymers to design a highly selective and conductive membrane for RED.

Cataloged from PDF version of article. This study focuses on both epitaxial growths of InxGa1-xN epilayers with graded In content, and the performance of solar cells structures grown on sapphire substrate by using metal organic chemical vapor deposition. The high resolution X-ray and Hall Effect characterization were carried out after epitaxial InGaN solar cell structures growth. The In content of the graded InGaN layer was calculated from the X-ray reciprocal space mapping measurements. Indium contents of the graded InGaN epilayers change from 8.8 to 7.1 % in Sample A, 15.7-7.1 % in Sample B, and 26.6-15.1 % in Sample C. The current voltage measurements of the solar cell devices were carried out after a standard micro fabrication procedure. Sample B exhibits better performance with a short-circuit current density of 6 mA/cm(2), open-circuit voltage of 0.25 V, fill factor of 39.13 %, and the best efficiency measured under a standard solar simulator with one-sun air mass 1.5 global light sources (100 mW/cm(2)) at room temperature for finished devices was 0.66 %.

Cataloged from PDF version of article. Rutile TiO2 nanorods on fluorine-doped thin oxide glass substrates via the hydrothermal technique were synthesized and decorated with a sputtered CdTe layer to fabricate a core-shell type n-TiO2/p-CdTe solar cell. Absorbance spectrum verified the absorption contribution of both TiO2 and CdTe to the absorption process. The solar cell parameters, such as open circuit voltage, short circuit current density, fill factor and power conversion efficiency were found to be 0.34 V , 1.27 mA cm(-2), 28% and 0.12%, respectively. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We characterize the surface passivation properties of ultrathin titanium oxide (TiO x ) films deposited by atomic layer deposition (ALD) on crystalline silicon by means of carrier lifetime measurements. We compare different silicon surface treatments prior to TiO x deposition, such as native silicon oxide (SiO y ), chemically grown SiO y and thermally grown SiO y . The best passivation quality is achieved with a native SiO y grown over 4 months and a TiO x layer thickness of 5 nm, resulting in an effective lifetime of 1.2 ms on 1.3 Ωcm p-type float-zone silicon. The measured maximum lifetime corresponds to an implied open-circuit voltage ( iV oc ) of 710 mV. For thinner TiO x layers the passivation quality is reduced, however, samples passivated with only 2 nm of TiO x still show a lifetime of 612 μs and an iV oc of 694 mV. The contact resistivity of the TiO x including the SiO y interlayer between the silicon wafer and the TiO x is below 0.8 Ωcm 2 . The combination of excellent surface passivation and low contact resistivity has the potential for silicon solar cells with efficiencies exceeding 26%.

The nature and dynamics of acceptor states in solution-processed Cu2ZnSn(S,Se)4 (CZTSSe) thin films are investigated by variable temperature photoluminescence (PL) and electrical impedance spectroscopy. Highly pure I-4 phase CZTSSe with the composition Cu1.6ZnSn0.9(S0.23Se0.77)4 is synthesized by sequentially spin coating of dimethyl-formamide/isopropanol solutions containing metal salts and thiourea onto Mo coated glass, followed by annealing in an Se atmosphere at 540 °C. As-annealed films are highly compact with a thickness of 1.3 μm and grain sizes above 800 nm, with a band gap of 1.18 eV. Photovoltaic devices of 0.25 cm2 with the architecture glass/Mo/CZTSSe/CdS/i-ZnO/Al:ZnO demonstrate a power conversion efficiency reaching up to 5.7% in the absence of an anti-reflective coating. Under AM 1.5G illumination at 296 K, the best device shows a 396 mV open-circuit voltage (VOC), 27.8 mA cm-2 short-circuit current (JSC) and 52% fill factor (FF). The overall dispersion of these parameters is under 15% for a total of 20 devices. In the near IR region, PL spectra are dominated by two broad and asymmetrical bands at 1.14 eV (PL1) and 0.95 eV (PL2) with characteristic power and temperature dependences. Analysis of the device electrical impedance spectra also reveals two electron acceptor states with the same activation energy as those observed by PL. This allows assigning PL1 as a radiative recombination at localized copper vacancies (VCu), while PL2 is associated with CuZn antisites, broadened by potential fluctuations (band tails). The impact of these states on device performance as well as other parameters, such as barrier collection heights introduced by partial selenization of the back contact, are discussed. © 2017 The Royal Society of Chemistry. Engineering and Physical Sciences Research Council, EPSRC: EP/L017792/1 Institute of Advanced Studies, University of Bristol, IAS: EP/K035746/1 DT, JWB and DJF are indebted to the Engineering and Physical Sciences Research Council (EPSRC) funded PVTEAM grant (EP/L017792/1). DJF acknowledges Institute of Advanced Studies of the University of Bristol support of a University Research Fellowship 2016. Impedance analysis was performed with a Solartron analyzer procured under EPSRC CDT Capital grant EP/K035746/1. Microscopic imaging and analysis were done at the Chemical Imaging Facility, University of Bristol, with equipment funded by EPSRC Grant ‘‘Atoms to Applications’’ (EP/K035746/1). The authors are grateful for measurement facilities provided at CREST, Loughborough University and the Department of Physics, SUPA, Strathclyde University.

Two types of Cu(In,Ga)Se2 (CIGS) solar cells, both designed for implementation in CIGS modules, were subjected to temperatures between 25C and 105C. Simultaneous exposure to AM1.5 illumination allowed the measurement of their electrical parameters at these temperatures. These two types of solar cells, produced with different deposition routes on soda lime glass (SLG) and polyimide (PI) substrates, showed large variations in the temperature dependency of their electrical parameters. It was shown that the temperature dependency of the open circuit voltage (Voc) was dependent on its room temperature value: a high Voc at 25 °C led to a slower loss of Voc when the temperature was increased. For the Voc, the normalised temperature dependency varied between -0.28%/°C and -0.47%/°C, which is in agreement with the literature. The temperature dependency of the short circuit current density (Jsc) showed more surprising results: while the PI samples had the expected positive temperature dependency (0.03 to 0.32%/°C), the SLG samples showed a small negative impact of increasing temperature (-0.01 to -0.05%/°C). A correlation between the temperature dependencies of the Jsc and the ideality factor n was observed. Therefore, this difference in the temperature dependence of the Jsc could be caused by increased recombination for the SLG samples. Furthermore, the temperature coefficients of the fill factor (negative), efficiency (negative), and the series (slightly negative) and shunt (negative) resistances were calculated.

Core-shell PbS/Sn:In2O3 and branched PbIn2S4/Sn:In2O3 nanowires have been obtained via the deposition of Pb over Sn:In2O3 nanowires and post growth processing under H2S between 100 C-200 C and 300 C-500 C respectively. The PbS/Sn:In2O3 nanowires have diameters of 50-250 nm and consist of cubic PbS and In2O3 while the PbIn2S4/Sn:In2O3 nanowires consist of PbIn2S4 branches with diameters of 10-30 nm and an orthorhombic crystal structure. We discuss the growth mechanisms and also show that the density of electrons in the n-type Sn:In2O3 core is strongly dependent on the thickness of the p-type PbS shell, which must be smaller than 30 nm to prevent core depletion, via the self-consistent solution of the Poisson-Schr�dinger equations in the effective mass approximation. The PbS/Sn:In2O3 and PbIn2S4/Sn:In2O3 nanowire networks had resistances of 100-200 Ω due to the large carrier densities and exhibited defect related photoluminescence at 2.2 eV and 1.5 eV respectively. We show that PbS in contact with polysulfide electrolyte has ohmic like behavior but the PbS/Sn:In2O3 nanowires gave, rectifying current voltage characteristics as a counter electrode in a quantum dot sensitized solar cell using a conventional ITO/TiO2/CdS/CdSe photo anode, an open circuit voltage of ≈0.5 V, and short circuit current density of ≈1 mA cm-2. In contrast the branched PbIn2S4/Sn:In2O3 nanowires exhibited a higher current carrying capability of ≈7 mA cm-2 and higher power conversion efficiency of ≈2%. � 2016 IOP Publishing Ltd. 28

Improving the efficiency of organic solar cells requires atomic insight into the interface electronic band alignment of the donor and acceptor moieties composing the device. In this article, we use ab initio calculations, with inclusion of long-range (van der Waals) interactions, to address the solid-state properties of a bulk heterojunction heterointerface between a single ordered layer of PCBM molecules adsorbed on a clean P3HT crystalline polymer. The studied interface model allowed us to focus on the basic mechanisms responsible for charge polarization and migration at the interface and to refer the energies of both moieties to the same origin. After the accurate evaluation of the relative energy positions of the near-gap electronic levels in the PCBM/P3HT complex and of the optical spectra useful for determining the nature of the electronic states, we analyzed the effect of uniaxial stress on the band alignment, and we found that both the polymer band gap and the offset between the LUMO levels of the donor and the acceptor materials decrease for compressive stress. This suggests that the donor band gap can be reduced, thus increasing solar energy harvest, and that the open-circuit voltage of the system can be tuned to improve the efficiency of PCBM/P3HT-based solar cell devices.

The Sb2S3-sensitized photoelectrochemical cells (Sb2S3–SPECs) in cobalt electrolyte were fabricated by depositing Sb2S3 on the macroporous TiO2 nanorods electrodes and consecutively spin-coating P3HT (Poly-3-hexylthiophene) interlayer to relieve the mass transport problem at vicinity of Sb2S3 and cobalt redox couples and reduce the backward recombination. Through the introduction of P3HT interlayer, we could greatly enhance the power conversion efficiency of Sb2S3–SPEC to 4.2% at 1 sun illumination, whereas the Sb2S3–SPEC without P3HT interlayer exhibits 3.2% of device efficiency. The electrochemical impedance analysis let us know that the improved device performance was mainly attributed to the reduced backward recombination building up the higher open circuit voltage.

The photovoltaic characteristics of a type II staggered heterojunction in the GaSb/GaInAsSb/GaAlAsSb system were studied. The dark current and R 0 A product were investigated at different temperatures. The current–voltage characteristics of n -GaSb/ n -GaInAsSb/ p -GaAlAsSb heterostructures were investigated at room temperature in the photovoltaic mode under illumination by light with wavelength of 0.95–1.0 μm and different intensities. A short-circuit current and an open circuit voltage as a function of intensity of incident light in photovoltaic mode were studied.

In this paper, a new technique using a Current Shunt and a Micropotentiometer has been used to study the electrical performance of a large area multicrystalline silicon solar cell at outdoor conditions. The electrical performance is mainly described by measuring both cell short circuit current and open circuit voltage. The measurements of this cell by using multimeters suffer from some problems because the cell has high current intensity with low output voltage. So, the solar cell short circuit current values are obtained by measuring the voltage developed across a known resistance Current Shunt. Samples of the obtained current values are accurately calibrated by using a Micropotentiometer (μpot) thermal element (TE) to validate this new measuring technique. Moreover, the solar cell open circuit voltage has been measured. Besides, the cell output power has been calculated and can be correlated with the measured incident radiation.

WOS:000386242500120 Lithium salt (LiCl, LiBr, LiI, or LiNO3) and a non-ionic surfactant (such as 10-lauryl ether, C12E10) form lyotropic liquid crystalline (LLC) mesophases in the presence of a small amount of water. The mesophases can be prepared as gels by mixing all the ingredients in one pot or in the solution phase that they can be prepared by coating over any substrate where the LLC phase is formed by evaporating excess solvent. The second method is easier and produces the same mesophase as the first method. A typical composition of the LLC phases consists of 2-3 water per salt species depending on the counter anion. The LiI-C12E10 mesophases can also be prepared by adding I-2 to the media to introduce an I-/I-3(-) redox couple that may be used as a gel-electrolyte in a dye-sensitized solar cell. Even though the mesophases contain a large amount of water in the media, this does not affect the cell performance. The water molecules in the mesophase are in the hydration sphere of the ions and do not act like bulk water, which is harmful to the anode of the dye-sensitized solar cells (DSSC). There are two major drawbacks of the salt-surfactant LLC mesophases in the DSSCs; one is the diffusion of the gels into the pores of the anode electrode and the other is the low ionic conductivity. The first issue was partially overcome by introducing the gel content as a solution and the gelation was carried in/over the pores of the dye modified titania films. To increase the ionic conductivity of the gels, other salts (such as LiCl, LiBr, and LiNO3) with better ionic conductivity were added to the media, however, those gels behave less effectively than pure LiI/I-2 systems. Overall, the DSSCs constructed using the LLC electrolyte display high short circuit current (I-sc of around 10 mA), high open circuit voltage (V-oc of 0.81 V) and good fill factor (0.69) and good efficiency (3.3%). There is still room for improvement in addressing the above issues in order to enhance the cell efficiency by developing new methods of introducing the gel-electrolytes into the mesopores of the anode electrode.

In this paper, we report an organic semiconductor based flexible thermogalvanic cell for conversion of heat and light energy into electric power. This thermogalvanic cell has been fabricated using a eco-friendly, affordable and commercially available organic material known as an orange dye (C17H17N5O2), which is soluble in water. The thermogalvanic cell consists of a Carbon/aqueous solution of orange dye/Carbon structure. The cell contains a flexible polymer tube casing, filled with a 5 wt% organic semiconductor orange dye aqueous solution and carbon-electrodes. Gradient of temperature (ΔT) up to 28 K was created by low power electric heater and up to 6 K by illumination. It was found that at ΔT = 8 K, the open-circuit voltage (V oc ), short-circuit current (I sc ) and Seebeck coefficient were in the range of −(31–32) mV, −(2.6–2.7) µA and −(3.8–3.9) mV/K, respectively. The thermogalvanic cell holds the promise of potential use in low-power applications (e.g. medical) and temperature gradient measurement. This publication was made possible by PDRA Grant No. PDRA1-0117-14109 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. Scopus

Here, we report on the optimization and chemical doping of reduced graphene oxide-silicon (rGO-Si) solar cells. Graphene oxide films were produced using a scalable vacuum filtration method and reduced via thermal annealing. The rGO films were used to make Schottky junction solar cells. The effect of rGO film thickness on solar cell performance was investigated, with short-circuit current densities and open-circuit voltages both tunable through the control of film thickness. Chemical doping of the rGO-Si solar cells, with varying annealed temperatures and thicknesses, was found to increase the cell power conversion efficiency by up to 220%, highlighting the importance of controlling the Fermi level of the rGO. These results indicate that there remains much potential for rGO-Si solar cells to compete with more traditional graphene-Si solar cells made with graphene produced using other methods. Refereed/Peer-reviewed

Perovskite solar cells (PSCs) are evolving with an impressive pace, emerging as the most promising next-generation photovoltaic devices. Nevertheless, beside these enormous progresses, the stability of PSCs remains one of the major problems to be challenged, because the most commonly used hole transporting material (HTM), the 2,2′,7,7′-Tetrakis-(N,N-di-4-methoxyphenylamino)−9,9′-spirobifluorene (Spiro-OMeTAD), suffers long-term stability. Here, we tackle this long-lasting issue exploiting reduced graphene oxide (RGO), prepared by an easy and efficient reduction method, as HTM in PSCs. We carried out endurance tests over 1987 h of shelf life and 120 h of light soaking. The PSCs based on RGO have shown power conversion efficiency (PCE) of 6.6%, outperforming the ones achieved with the Spiro-OMeTAD (PCE=6.5%), after the shelf life test. The light soaking test confirmed the better durability of RGO-based PSCs with respect to the Spiro-OMeTAD ones, the latter showing a reduction in PCE 2.7 times higher than the RGO-based cells. Moreover, we demonstrate by Open Circuit Voltage Decay measurements that RGO, beside the HTM function, acts also as an anti-recombination layer, reducing the charge carriers recombination pathways and, hence, increasing their lifetime.

We report on ion-implanted, inkjet patterned back junction back contact silicon solar cells with POLysilicon on Oxide (POLO) junctions for both polarities – n+ doped BSF and p+ doped emitter. The recombination behavior is investigated at two different processing stages: before and after trench separation of p+ and n+ regions within polysilicon (poly-Si). Before trench separation, we find a systematic dependence of the recombination behavior on the BSF index, i.e. the p+n+-junction meander length in the poly-Si. Obviously, recombination at the p+n+-junction in the poly-Si limits the implied open circuit voltage Voc,impl. at one sun illumination and the implied pseudo fill factor pFFimpl. to 695 mV and 80%, respectively. After trench isolation, however, Voc,impl (pFFimpl.) values increase up to 730 mV (85.5%), corresponding to a pseudo-efficiency of 26.2% for an assumed short circuit current density Jsc of 42 mA/cm2. We demonstrate a photolithography-free back junction back contacted solar cell with p-type and n-type POLO junctions with an in-house measured champion efficiency of 23.9% on a designated area of 3.97 cm2. This efficiency is mainly limited by the imperfect passivation in the undoped trench regions and at the undoped front side. EU/FP7/608498

WOS: 000389102500082, In this paper, a numerical investigation of the effects of thickness of absorber and buffer layers for a typical CIGS based solar cell was carried out for the first time, employing the wxAMPS software which is a new custom-designed software package for solar cell simulation. We have examined how the output parameters change with absorber and buffer thicknesses and suggested four different cell structures. By using the baseline structure, an optimum band gap value of 1.4 eV was determined for the CIGS absorber layer prior to do thickness study. Optimum absorber thickness value has been determined as 2500 nm from the simulation results. Spectral response of the cell decreased with increasing thickness in blue region. The influence of buffer layer thickness was investigated and it was found that most of the photo-generated carriers are collected by a thinner CdS layer. A significant decrease in current density, open circuit voltage and conversion efficiency occurred with increasing buffer layer thickness. This behavior was attributed to a decrease in the number of collected carriers due to the recombination of electron-hole pairs proceeded from the absorbed photons in the CdS bulk for large thickness. As a result, efficiencies around 27% were obtained through optimization while that of baseline structure was 25%. Our results have shown that the suggested structures both produce higher efficiencies than that of baseline structure and may lead to produce more efficient CIGS-based thin film solar cells. (C) 2016 Elsevier GmbH. All rights reserved., Scientific Research Commission of Mustafa Kemal University [12661], The authors thank to the original developer of wxAMPS, Dr. Y Liu in Nankai University, for valuable discussions, and Dr. Fonash's group at Pennsylvania State University (PSU) which they first developed AMPS-1D. A great appreciate is sent to Golden Software, LLC. This study is conducted with support of Scientific Research Commission of Mustafa Kemal University (Project No: 12661).

Nanostructured solar cells are a promising area of research for the production of low cost devices that may eventually be capable of complementing or even replacing present technologies in the field of solar power generation. The use of quantum dots (QDs) in solar cells has evolved from being simple absorbers in dye-sensitized solar cells to sustaining the double functions of absorbers and carrier transporters in full solid state devices. In this work, we use both optical and electrical measurements to explore the diffusion limitations of carrier transport in cells made of a heterostructure combining lead sulfide (PbS) QDs as absorbers and hole carrier and zinc oxide nanowires as electron carrier material. The results show efficient charge collection along the PbS-QD/ZnO nanowire (NW) hybrid structure. This is because of the formation of band bending in the ZnO collector, allowing efficient charge separation and spatially well-separated carrier pathways, yielding a hole transportation of over 1 μm. We have also found a limitation in open-circuit voltage (Voc) associated with band bending in the ZnO collector. This research is supported by the Japan Science and Technology Agency (JST) thorough its “Funding Program for Core Research for Evolutional Science and Technology (339-5 CREST)” and New Energy and Industrial Technology Development Organization (0520002 NEDO) and the Ministry of Economy, Trade and Industry (METI), Japan. The work is also supported by Generalitat Valenciana (ISIC/2012/008 Institute of Nanotechnologies for Clean Energies, PROMETEO/2014/020). This work is partly supported by JX Nippon Oil & Energy Corporation. Cordial thanks are due to Toyo Corporation for the use of the ModuLab system (Solartron) for obtaining IMPS data.

In this present work, Multi-walled carbon nanotubes (MWNTs) with different content by weight (10%, 20%, 30%, 50% and 70%) are introduced into Polypyrrole nanoparticles (PPy NP) matrix and fabricated as Pt free counter electrodes (CEs) for dye-sensitized solar cell (DSSC). For comparison DSSCs using pristine PPy NP, MWNTs and Platinum (Pt) were also fabricated. The incorporation of MWNTs acts as conductive channel and co-catalyst to the PPy NP CEs in the reduction of I-3 to I- . The electrochemical catalytic activities of different CEs were analysed by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) and photovoltaic performance was studied under standard AM 1.5 sunlight illumination. It was observed that incorporation of MWNTs in the PPy NP CE greatly enhanced the catalytic activity for I-3 reduction and significantly reduced the charge transfer resistance in the PPy NP/MWNTs composite CE finally improving short-circuit photocurrent density, fill factor, open circuit voltage and power conversion efficiency of DSSC. DSSC fabricated from PPy NP/MWNTs composite CE with 50% MWNTs content reached the highest photoconversion efficiency of 5.80% which is 91% that of Pt CE based DSSC (6.37%). � 2015 American Scientific Publishers All rights reserved.

Aftera briefreview of therecent evolvement oforganic-silicon heterojunction solar cells,we present here our latest measurements of the saturation current densities (J0) and contact resistances (RC) of crystalline silicon (c-Si)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) junctions. We determine the J0values by means of contactless carrier lifetime measurements and theRCvalues by comparing sheet resistance measurements with numerical device simulations of the corresponding test structure. Application of an adopted PEDOT:PSS blend and an optimized silicon surface treatmentresults in a minimalJ0value of46 fA/cm2, limiting the solar cell open-circuit voltage to Voc_limit=708 mV, and a minimal RCvalue of 100 mΩcm2. Our optimized silicon surface pre-treatment in combination with the adapted PEDOT:PSS blendare successfully implemented into a cell process with the PEDOT:PSS layer located at the rear surface (the so-called ‘BackPEDOT concept’). Record-high efficiencies of 18.3% and of 20.6% are achieved onn-type silicon and onp-type silicon wafers, respectively. Finally, we compare the internal quantum efficiency of our champion BackPEDOT solar cell with that of a state-of-the-art Al2O3/SiNx-passivated PERC solar cell.

Material layers at electrode/semiconductor interfaces are fundamental for the photovoltaic properties of polymer solar cells. The relationship between open-circuit voltage (VOC) and the work function ($phi$) of these interface layers is still a matter of debate. Simulations, together with experiments on over more than 20 cell architectures based on P3HT:PC60BM, enabled us to analyze the physical dependence of VOC on $phi$. In particular, when the work function of the contacts is well inside the gap we observe that performance depends strongly on even small variations of $phi$. On the other hand, when it approaches the energy levels of the semiconducting polymers, device operation becomes the most efficient and less sensitive to variations in $phi$. Furthermore, by varying the Gaussian density of states (DOS) of the active blend we were able to show that VOC performance depends significantly also on the DOS. Our study based on the simultaneous variation of transport layers represents a promising method to optimize the design and performance of polymer solar cells.

A multilayered triboelectric nanogenerator (MULTENG) that can be actuated by acoustic waves, vibration of a moving car, and tapping motion is built using a 3D-printing technique. The MULTENG can generate an open-circuit voltage of up to 396 V and a short-circuit current of up to 1.62 mA, and can power 38 LEDs. The layers of the triboelectric generator are made of polyetherimide nanopillars and chalcogenide core-shell nanofibers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

c ¨¨ ¨ Abstract Conjugated polymeryfullerene plastic solar cells of the first generation were consisting of two distinct layers, made of the donor polymer and of the acceptor fullerene, respectively, sandwiched between two metal contacts. By mixing the polymer and the fullerene components, thus replacing a single flat junction with an interpenetrating network bulk-heterojunction, the device efficiency was dramatically improved. As a further step to proceed with the development of plastic solar cells, we developed the bulk diffusion bilayer approach, allowing the creation of donor-acceptor diffused interfaces with less restrictions to the phase compatibility of the two components. For a novel series of fullerenes, the bulk diffusion bilayer approach is shown to yield devices with comparable efficiencies as the blend bulk heterojunction approach. Bulk-heterojunction devices show unusually high open circuit voltage (V ) values. These values cannot be explained by the metal-insulator-metal (MIM) model that has been OC often used for organic light emitting diodes. In order to investigate the origin of the V in bulk-heterojunction plastic solar cells, OC we have prepared PPV based devices varying both the metal negative contact and the fullerene acceptor. Fullerene derivatives with varying acceptor strength, (i.e. the first reduction potential ) were used as electron acceptors in bulk-heterojunction plastic solar cells produced with the blend as well as the diffusion bilayer approach. The open circuit voltage of the devices was found to correlate directly with the acceptor strength of the fullerenes, while it was rather insensitive to variations in the workfunction of the negative electrode metal. These results suggest that the quasi-Fermi level of the fullerene pins the Fermi level of the evaporated negative metal contact. 2002 Elsevier Science B.V. All rights reserved.

CuSCN is proposed as a cost-competitive hole selective contact for the emerging organo-metal halide perovskite-based solar cells. The CuSCN films have been deposited by a solution casting technique, which has proven to be compatible with the perovskite films, obtaining planar-like heterojunction-based glass/FTO/TiO2/CH3NH3PbI3−xClx/CuSCN/Au solar cells with a power conversion efficiency of 6.4%. Among the photovoltaic parameters, the fill factor (i.e. 62%) suggests good carrier selectivity and, therefore, efficient functionality of the TiO2 and CuSCN charge carrier selective contacts. However, the open-circuit voltage (Voc), which remains low in comparison with the state of the art perovskite-based solar cells, appears to be the main limiting parameter. This is attributed to the short diffusion length as determined by impedance spectroscopy. However, the recombination losses are not only affected by the CuSCN, but also by the perovskite film. Indeed, variations of 20 °C in the thermal annealing of the perovskite films result in changes larger than 200 mV in the Voc. Furthermore, a detailed analysis of the quantum efficiency spectra contributes significant insights into the influence of the selective contacts on the photocurrent of the planar heterojunction perovskite solar cells.

One of the factors limiting the performance of organic solar cells (OSCs) is their large energy losses (E loss) in the conversion from photons to electrons, typically believed to be around 0.6 eV and often higher than those of inorganic solar cells. In this work, a novel low band gap polymer PIDTT-TID with a optical gap of 1.49 eV is synthesized and used as the donor combined with PC71BM in solar cells. These solar cells attain a good power conversion efficiency of 6.7% with a high open-circuit voltage of 1.0 V, leading to the E loss as low as 0.49 eV. A systematic study indicates that the driving force in this donor and acceptor system is sufficient for charge generation with the low E loss. This work pushes the minimal E loss of OSCs down to 0.49 eV, approaching the values of some inorganic and hybrid solar cells. It indicates the potential for further enhancement of the performance of OSCs by improving their V oc since the E loss can be minimized. Refereed/Peer-reviewed