Efficiency Loss In Cells Research Articles

Superior specific capacity and energy density simultaneously achieved by Sr/In co-deposition behavior of Mg-Sr-In ternary alloys as anodes for Mg-Air cells

In this work, the combined addition of strontium/indium (Sr/In) to the magnesium anode for Mg-Air Cells is investigated to improve discharge performance by modifying the anode/electrolyte interface. Indium exists as solid solution atoms in the α-Mg matrix without its second-phase generation, and at the same time facilitates grain refinement, dendritic segregation and Mg17Sr2-phases precipitation. During discharge operation, Sr modifies the film composition via its compounds and promoted the redeposition of In at the substrate/film interface; their co-deposition behavior on the anodic reaction surface enhances anode reaction kinetics, suppresses the negative difference effect (NDE) and mitigates the “chunk effect” (CE), which is contributed to uniform dissolution and low self-corrosion hydrogen evolution rate (HER). Therefore, Mg-Sr-xIn alloy anodes show excellent discharge performance, e.g., 0.5Sr-1.0In shows an average discharge voltage of 1.4234 V and a specific energy density of 1990.71 Wh kg−1 at 10 mA cm−2. Furthermore, the decisive factor (CE and self-discharge HE) for anodic efficiency are quantitively analyzed, the self-discharge is the main factor of cell efficiency loss. Surprisingly, all Mg-Sr-xIn anodes show anodic efficiency greater than 60% at high current density (≥10 mA cm−2), making them excellent candidate anodes for Mg-Air cells at high-power output.

Estimation of future changes in photovoltaic potential in Australia due to climate change

Solar photovoltaic (PV) energy is one of the fastest growing renewable energy sources globally. However, the dependency of PV generation on climatological factors such as the intensity of radiation, temperature, wind speed, cloud cover, etc can impact future power generation capacity. Considering the future large-scale deployment of PV systems, accurate climate information is essential for PV site selection, stable grid regulation, planning and energy output projections. In this study, the long-term changes in the future PV potential are estimated over Australia using regional climate projections for the near-future (2020–2039) and far-future (2060–2079) periods under a high emission scenario that projects 3.4 °C warming by 2100. The effects of projected changes in shortwave downwelling radiation, temperature and wind speed on the future performance of PV systems over Australia is also examined. Results indicate decline in the future PV potential over most of the continent due to reduced insolation and increased temperature. Northern coastal Australia experiences negligible increase in PV potential during the far future period due to increase in radiation and wind speed in that region. On further investigation, we find that the cell temperatures are projected to increase in the future under a high emission scenario (2.5 °C by 2079), resulting in increased degradation and risks of failure. The elevated cell temperatures significantly contribute to cell efficiency losses, that are expected to increase in the future (6–13 d yr−1 for multi-crystalline silicon cells) mostly around Western and central Australia indicating further reductions in PV power generation. Therefore, long-term PV power projections can help understand the variations in future power generation and identify regions where PV systems will be highly susceptible to losses in Australia.

Pt Surface Oxides and Oxygen Reduction Reaction Kinetics Under Dynamic PEM Fuel Cell Operation

Surface oxides formed on Pt electrocatalysts at high potential (>0.8 V) suppress the oxygen reduction reaction (ORR) activity. Reduced activity due to surface oxide contributes to a noticeable amount of fuel cell efficiency loss.[1] While mathematical models were developed, , agreement with experimental results is limited to standard steady-state conditions.[2] A kinetic model is needed to explain a dynamically operating fuel cell, where the catalyst is often exposed to a range of temperature, humidity, and potential over time.Here, we conducted time-resolved measurements of ORR kinetics and oxide coverage for Pt and PtCo cathode catalysts under various temperature and relative humidity (RH). We found that the dependance of Pt oxide (PtO) coverage on the RH can be expressed by a modified Langmuir adsorption isotherm. In contrast to conventional understanding that RH-dependence of PtO coverage is due to water being the reactant, our results suggest that the dependency is due to ionomer co-adsorption on Pt surface. Analysis of the ORR activity and PtO coverage suggests two types of PtO. The time-resolved measurement allowed us to deconvolute the two PtO types and develop a kinetic model that gives improved prediction capability over a range of dynamic operation commonly observed in a real fuel cell.This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271. Reference [1] J. Mitzel, Q. Zhang, P. Gazdzicki, K.A. Friedrich, J. Power Sources, 488 (2021) 229375.[2] P. Subramanian, T. A. Greszler, J. Zhang, W. Gu, and R. Makharia, Journal of The Electrochemical Society, 159 (5), B531-B540 (2012)

Design investigation on 100 μm-thickness thin silicon PERC solar cells with assistance of machine learning

Thin crystalline silicon passivated emitter and rear cell (PERC) solar cells are a very prospective technology for next-phase photovoltaic development due to the potential of high cost effectiveness. The reduction of silicon wafer thickness can significantly save the costs, but there is a loss of cell efficiency if cell design is not conducted. For the thinned 100 μm-thickness PERC solar cells without design, the efficiency loss is pronounced from commercial 180 μm-thickness. In this paper, we have designed and optimized SiO2/SiNx/SiNx/SiOx thin films (here two SiNx layers have different refractive index) on the front surface and SiNx/SiOx thin films on the back surface for the standard front single-sided textured PERC cells. Based on this, we further design and investigate the case of double-sided textured PERC solar cells. Compared with the reference cell, the present designs can lead to the short-circuit current density increase by 0.6 mA/cm2 and the open-circuit voltage enhancement by 10 mV for the front textured case, which causes the efficiency gain of 0.7% from 21.6% to 22.3%. For the double-sided textured cells, the efficiency has an extra increase of 0.6% from 22.3% to 22.9%. Finally, we have constructed the efficiency prediction model by using the multilayer perceptron algorithm in machine learning. It is found from the SHAP values that a significant effect of the front SiNx thickness is observed to predict the performance of the PERC cells.

Effects of Moisture-Proof Back Passivation Layers of Al2O3 and AlxTi1-xOy Films on Efficiency Improvement and Color Modulation in Transparent a-Si:H Solar Cells.

In this study, the back passivation layers (BPLs) were developed to protect hydrogenated amorphous silicon (a-Si:H) thin films of transparent solar cells from humidity and contaminants. Metal oxide compound films with Al (Al2O3) and Ti (AlxTiyOz (ATO)) were fabricated by plasma-enhanced atomic layer deposition for the BPLs on transparent solar cells. The BPLs of Al2O3 films applied to the transparent solar cells were deposited in different thicknesses to evaluate the performance, and the ATO film thickness was fixed at 30 nm. Even at the thinnest thickness of 30 nm, the water vapor transmission rates of BPLs were very low at 1.96 × 10-3 (Al2O3) and 1.23 × 10-2 g/m2·day (ATO). In addition to moisture protection, measures of cell performance, including open-circuit voltage and short-circuit current density, were improved by blocking the leakage current and through the optical interference effects of the BPLs. The solar cell with ATO BPLs exhibited an increase in efficiency of more than 12% compared with those of conventional reference cells. Furthermore, by varying the refractive index and thickness of the BPLs, the reflection and transmission spectra were modulated to implement various cell colors without serious loss in cell efficiency.

PEM fuel cells fed by hydrogen from ethanol dehydrogenation reaction: Unveiling the poisoning mechanisms of the by-products

This work investigates the influence of hydrogen contaminated with the main by-products of the ethanol dehydrogenation reaction, i.e. ethyl acetate, acetaldehyde and unreacted ethanol, on the anode performance of a proton exchange membrane fuel cell employing different catalysts, aiming at understanding and minimizing the efficiency losses caused by these molecules. Pt-W/C and Pt-Sn/C catalysts were investigated, having Pt/C as reference, which were chosen due their ability to oxidize small organic molecules without breaking of CC bonds and without producing strong poisoning intermediates (i.e. less prone to have its active sites blocked by side reactions). Results evidence that anode catalysts that presents lower activity for small organic molecules oxidation and/or weaker reactant adsorption, which is the case of Pt-Sn/C, are best suited for PEMFC systems directly fed by hydrogen from ethanol dehydrogenation reaction. It is also found that crossover of the considered by-products from the anode towards the cathode also has a major impact on fuel cell efficiency losses.

Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment.

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the Earth's atmosphere. So-called 'solar fuel' devices, currently developed for terrestrial applications in the quest for realizing a sustainable energy economy on Earth, provide promising alternative systems to existing air-revitalization units employed on the International Space Station (ISS) through photoelectrochemical water-splitting and hydrogen production. One obstacle for water (photo-) electrolysis in reduced gravity environments is the absence of buoyancy and the consequential, hindered gas bubble release from the electrode surface. This causes the formation of gas bubble froth layers in proximity to the electrode surface, leading to an increase in ohmic resistance and cell-efficiency loss due to reduced mass transfer of substrates and products to and from the electrode. Recently, we have demonstrated efficient solar hydrogen production in microgravity environment, using an integrated semiconductor-electrocatalyst system with p-type indium phosphide as the light-absorber and a rhodium electrocatalyst. By nanostructuring the electrocatalyst using shadow nanosphere lithography and thereby creating catalytic 'hot spots' on the photoelectrode surface, we could overcome gas bubble coalescence and mass transfer limitations and demonstrated efficient hydrogen production at high current densities in reduced gravitation. Here, the experimental details are described for the preparations of these nanostructured devices and further on, the procedure for their testing in microgravity environment, realized at the Bremen Drop Tower during 9.3 s of free fall.

Generating Oxygen Vacancies in MnO Hexagonal Sheets for Ultralong Life Lithium Storage with High Capacity.

The polar surface of (001) wurtzite-structured MnO possesses substantial electrostatic instabilities that facilitate a wurtzite to graphene-like sheet transformation during the lithiation/delithiation process when used in battery technologies. This transformation results in cycle instability and loss of cell efficiency. In this work, we synthesized MnO hexagonal sheets (HSs) possessing abundant oxygen vacancy defects (MnO-Vo HSs) by pyrolyzing and reducing MnCO3 HSs under an atmosphere of Ar/H2. The oxygen vacancies (Vos) were generated in the reduction process and have been characterized using a range of techniques: X-ray absorption fine structure, electron-spin resonance, X-ray absorption near edge structure, Artemis modeling, and R space Feff modeling. The data arising from these analyses inform us that the introduction of one Vo defect within each O atom layer can reduce the charge density by 3.2 × 10-19 C, balancing the internal nonzero dipole moment and rendering the wurtzite structure more stable, so inhibiting the change to a graphene-like structure. Density function theory calculations demonstrate that the incorporation of Vos sites significantly improves the charge accumulation around Li atoms and increases Li+ adsorption energies (-2.720 eV). When used as an anode material for lithium ion batteries, the MnO-Vo HSs exhibit high specific capacity (1228.3 mAh g-1 at 0.1 A g-1) and excellent cell cycling stabilities (∼88.1% capacity retention after 1000 continuous charge/discharge cycles at 1.0 A g-1).

Comparison of light-induced degradation and regeneration in P-type monocrystalline full aluminum back surface field and passivated emitter rear cells

This paper reports on a systematic and quantitative assessment of light induced degradation (LID) and regeneration in full Al-BSF and passivated emitter rear contact cells (PERC) along with the fundamental understanding of the difference between the two. After LID, PERC cells showed a much greater loss in cell efficiency than full Al-BSF cells (∼0.9% vs ∼0.6%) because the degradation in bulk lifetime also erodes the benefit of superior BSRV in PERC cells. Three main regeneration conditions involving the combination of heat and light (75 °C/1 Sun/48 h, 130 °C/2 Suns/1.5 h and 200 °C/3 Suns/30 s) were implemented to eliminate LID loss due to BO defects. Low temperature/long time (75 °C/48 h) and high temperature/short time (200 °C/30s) regeneration process was unable to reach 100% stabilization. The intermediate temperature/time (130 °C/1.5 h) generation achieved nearly full recovery and stabilization (over 99%) for both full Al-BSF and PERC cells. We discussed the effect of temperature, time and suns in regeneration mechanism for two cells.

Colored a-Si:H transparent solar cells employing ultrathin transparent multi-layered electrodes

We fabricated hydrogenated amorphous silicon (a-Si: H) transparent solar cells using ultrathin transparent multi-layered electrodes (TMEs) as rear-side transparent electrodes for building-integrated photovoltaic (BIPV) windows. Each TME included a bottom layer, thin Ag layer, and optoelectronic controlling layer (OCL). The TMEs were experimentally designed to have high transparency and conductance. The fabricated a-Si:H transparent solar cells showed optimal performance with a 6.36% power-conversion efficiency and 23.5% average transmittance (500–800nm) when TMEs with a thickness less than 160nm were incorporated. We demonstrated that the reflection color of the cell could be tuned without serious loss of cell efficiency by varying the thickness of the OCL. The backside colors were predicted to be the coordinates on a CIE 1931 chromaticity diagram using the reflection spectrum from the cell and emission spectrum of a 50W LED light source. The developed a-Si:H transparent solar cells exhibited high efficiency and show feasibility for incorporating various colors in the photovoltaic and aesthetic functionalities of BIPV windows.

20.8% industrial PERC solar cell: ALD Al2O3 rear surface passivation, efficiency loss mechanisms analysis and roadmap to 24%

PERC cell is currently entering the industrial crystalline silicon solar cell production lines. While there has been many reports focusing on research PERCs, this paper aims to present a cost-efficient PERC roadmap at fully industrial level, i.e. beyond the research and pilot lines. We present a systematic experimental study on the most important material and cell parameters for PERC, for instance, the key processes of ozone based ALD Al2O3 rear surface passivation and screen printed aluminum local back surface field are discussed in detail, especially highlighting the importance of the process integration. Industrial PERC cells using this roadmap have demonstrated average efficiency of 20.5% and champion efficiency of 20.8% with open circuit voltage of 660–666mV. Light-induced degradation analysis shows that the PERC cells are subject to bulk degradation and not to surface degradation. An anti-LID treatment processed by simultaneous applying forward voltages and anneal can drastically decrease LID. The cell efficiency loss mechanisms are analyzed based on the quantum efficiency measurement, suns-Voc tests and series resistance loss calculations. These are combined with PC1D and PC2D simulations to analyze recombination loss mechanisms present in the cells in order to promote viable solutions to extend the current industrial PERC cell efficiency to 24%.

Simplified Fabrication of n-type Cz-Si HIP-MWT+ Solar Cells with 20% Efficiency Using Laser Structuring

We present 6-inch n-type Cz-Si metal wrap through (MWT) solar cells with screen-printed and fired contacts achieving energy conversion efficiencies of 20%. In order to decrease the occurrence of leakage currents under forward operation to a minimum after applying reverse bias load, the structuring of the rear side phosphorus doping in the area of the external p-type contacts is necessary. The fabrication of these so-called n-type high-performance MWT+ (n-HIP-MWT+) solar cells is considerably simplified by using laser processes to locally structure the rear side phosphorus doping. The n-HIP-MWT+ cells fabricated with laser structuring achieve the same peak energy conversion efficiency of 20% as conventionally fabricated ones, which are manufactured using an elaborate inkjet-based masking process prior to phosphorus diffusion. The loss of cell efficiency after reverse biasing is decreased to – 0.1%abs independent of the structuring method, and is three times smaller than the one observed for cells without structuring of the phosphorus doping.

Invited; Light Induced Degradation in Compensated B-Doped Czochralski Silicon

Light induced degradation (LID) in B-doped Czochralski Si solar cells is a universal phenomenon, which reduces the conversion efficiency by 2-5% relatively. It is believed that Boron-Oxygen complexes are formed during light illumination, which are the effective recombination centers. Studies in the exclusively B-doped Si, B/Ga co-doped Si and p-type B/P compensated Si show that the saturated concentration (Nt*) of B-O defect is proportional to the B concentration (NB ) (or the net hole concentration p0 ) and the generation rate constant (Rgen ) proportional to p0 2 . Interestingly, the LID has also been found in n-type B/P compensated Si, which was supposed to be unlikely to happen. Hence, it brings out a fundamental question of whether the p- and n-type B-doped Si have the same formation mechanism of LID. In this presentation, we will report our recent work about LID in B-doped compensated Cz silicon. It is believed that the BO defect density in compensated silicon depends on the B concentration and the net doping concentration. Moreover, High B concentration in the compensated silicon results in very serious cell efficiency loss. Furthermore, The electrical parameters of the reference and compensated cells can get fully recovered by illumination at high temperatures. Moreover, the LID in n-type B-doped Cz silicon with thermal donors (TDs) compensation is also reported. The advantage of TDs compensation is able to obtain a variation of carrier density but with a constant NB . We find that the formation of B-O complex also occurs under the light illumination and can be annealed out quickly in the dark at 200 oC. The Nt* exhibits a nonlinear dependence on the majority carrier concentrations n0 , and the Rgen is independent on the n0 . The formation activation energy is determined to be 0.4 eV, identical to the value in p-type Si. Based on the results, we believe that the nature of LID in p- and n-type silicon should be the same.

Towards ultra-thin plasmonic silicon wafer solar cells with minimized efficiency loss.

The cost-effectiveness of market-dominating silicon wafer solar cells plays a key role in determining the competiveness of solar energy with other exhaustible energy sources. Reducing the silicon wafer thickness at a minimized efficiency loss represents a mainstream trend in increasing the cost-effectiveness of wafer-based solar cells. In this paper we demonstrate that, using the advanced light trapping strategy with a properly designed nanoparticle architecture, the wafer thickness can be dramatically reduced to only around 1/10 of the current thickness (180 μm) without any solar cell efficiency loss at 18.2%. Nanoparticle integrated ultra-thin solar cells with only 3% of the current wafer thickness can potentially achieve 15.3% efficiency combining the absorption enhancement with the benefit of thinner wafer induced open circuit voltage increase. This represents a 97% material saving with only 15% relative efficiency loss. These results demonstrate the feasibility and prospect of achieving high-efficiency ultra-thin silicon wafer cells with plasmonic light trapping.

An Evaluation of the Ethanol Oxidation Activity of Ternary Pt-Rh-SnO2 catalysts Prepared from the Vapor Phase

Ethanol holds promise as a non-toxic, transportable, energy dense (8kWh/kg), and fuel that, unlike hydrogen, is amenable to use in the existing fuel infrastructure. However, slow oxidation kinetics and incomplete CO2 formation, indicating unbroken C-C bonds at practical potentials, limit usage in a fuel cell. Incomplete formation of CO2, a complete 12 electron transfer, leads to the formation of adsorbed intermediates such as CO, acetaldehyde, and acetic acid. These intermediates can poison the catalyst surface leading to a loss in cell efficiency. The use of Pt/Rh/Sn ternary catalysts has proven promising owing to bi-functional, electronic, and synergistic effects between the constituents. The role of Rh is to cleave the C-C bond of ethanol, SnO2provides the OH species to oxidize intermediates (freeing the Pt and Rd sites), and Pt is for ethanol dehydrogenative adsorption [1]. Typical synthesis methods include polyol [2], Bönneman [3], co-impregnation-reduction [4], or cation-adsorption-reduction-galvanic displacement [5] techniques. Previous flame-based deposition of catalysts for ethanol oxidation have focused on Pt-Sn combinations and found that 10 wt.% Sn showed the best onset potential (~0.3V vs RHE) and largest oxidation peaks in 0.5 M H2SO4and 1 M ethanol at 1 mV/s [6]. Reactive spray deposition technology (RSDT) has been developed by Maric et al. to produce nanoparticles in vapor phase for catalysts comprised of Pt [7,8], IrxPt1-xO2-y, and IrxRu1-xO2-y [9]. In this work we extend recent studies on Pd-Ru and Pd cores made by the RSDT process, with subsequent Pt monolayer attachment by galvanic displacement, to the ternary Pt/Rh/Sn system. Elemental ratios of 3:1:3 and 3:2:3 are examined for their performance toward ethanol oxidation. Figure 1 shows the nodular morphology of Pt/Rh/Sn (3:2:3) as grown on a gas diffusion layer along with the XEDS elemental mapping. Strategies for electrode activation using potential cycling in HClO4, ethanol and CO stripping are discussed. Figure 2 is a plot of the CV after various pre-treatment approaches. The performance toward ethanol oxidation at room temperature and 60oC will be discussed in respect to chemical composition. A representative linear sweep voltammogram is shown in Figure 3. Infrared reflection-absorption spectroscopy (IRRAS) is explored to detail the EOR mechanism. Microscopy studies of the structure and chemical composition are presented.

Impact of the Band Offset for n-Zn(O,S)/p-Cu(In,Ga)Se$_{2}$ Solar Cells

The conduction-band offset (CBO) of the Zn(O, S)/Cu(In,Ga)Se2 heterojunction can play a significant role in the performance of solar cells. The individual electron affinities and bandgaps are controlled by the oxygen-to-sulfur and gallium-to-indium ratios, and the resulting offsets can range from +1.3 eV in the “spike” direction to -0.7 eV in the “cliff” direction if the full range of the two ratios is considered. The optimal CBO of near +0.3 eV can be achieved with various combinations of the two ratios. The traditional CdS emitter is near optimal for the commonly used 1.15-eV Cu(In,Ga)Se 2 (CIGS) but less optimal for higher Ga. The flexibility with Zn(O,S) emitters ranging from above 90% oxygen for CIS down to 50% oxygen for CGS allows an optimal CBO over the full gallium range. Assuming that other factors remain constant, the optimal offset should also be able to reduce the loss in cell efficiency between room temperature and temperatures more typical of field conditions by about 1% absolute.

Solar Cell Efficiency Losses Due to Impurities From the Crucible in Multicrystalline Silicon

The electrical material quality of multicrystalline (mc) silicon for photovoltaic applications suffers from crystal defects as well as from impurities that originate from the feedstock, the quartz crucible, and its coating. In this study, we investigate the influence of impurities from the crucible on efficiency losses in mc silicon solar cells, focusing on the limitation due to iron. The applicability of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX"> $p$</tex></formula> -type mc silicon, crystallized in G1 sized crucibles of industrial material quality and very pure electrically fused silica, for a high-efficiency solar cell process is examined by measuring lifetime and interstitial iron concentration in the wafers after different processing steps and by estimating the cell efficiency potential from injection-dependent bulk lifetime measurements. Interstitial iron concentrations extracted from 2-D simulations of iron precipitation at crystal defects and gettering during processing agree well with Fe <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$_{\rm i}$</tex></formula> measurements at different process stages and explain the observations. Efficiency losses are quantified to losses due to segregated impurities diffused into the silicon melt, losses due to decorated crystal defects and losses due to solid-state diffusion into the crystal. By using a high-purity crucible, losses are reduced significantly and an efficiency gain of 0.5% absolute is estimated to be attainable on wafers with edge region.

Assessment of the illumination dependency of Al2O3 and SiO2 rear‐passivated p‐type silicon solar cells

AbstractThis Letter discusses an important difference between positively charged SiO2 and negatively charged Al2O3 rear‐passivated p‐type Si solar cells: their illumination level dependency. For positively charged SiO2 rear‐passivated p‐type Si solar cells, a loss in short circuit current (JSC) and open circuit voltage (VOC) as a function of illumination level is mainly caused by parasitic shunting and a decrease in surface recombination, respectively. Hence, the relative loss in cell conversion efficiency, JSC, and VOC as a function of the illumination level for SiO2 compared to Al2O3 rear‐passivated p‐type Si solar cells has been measured and discussed. Subsequently, an exponential decay fit of the loss in cell efficiency is applied in order to estimate the difference in the energy output for both cell types in three different territories: Belgium (EU), Seattle and Austin (US). The observed trends in the difference in energy output between both cells, as a function of time of the year and region, are as expected and discussed. (© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Laser beam induced current measurements of Cd1−xZnxS/CdTe solar cells

The role of the window layer in Cd1−xZnxS/CdTe photovoltaic (PV) device structures was investigated using a triple wavelength laser beam induced current (LBIC) technique. Full pn structures were deposited using metal organic chemical vapour deposition (MOCVD). The triple wavelength LBIC technique allowed for the diagnostic analysis of carrier collection uniformity at 3 wavelength dependent photon penetration depths, δp. An assessment of the Cd1−xZnxS window layer film thickness and surface coverage showed a correlation between lateral device performance and window layer thickness distribution. Islands of thick Cd1−xZnxS were shown to increase localised blue absorption, correlating to isolated regions of increased red and IR photoresponse. Overall device open-circuit voltage, Voc is shown to demonstrate a linear dependence on thick (∼300nm) Cd1−xZnxS surface coverage. Voc and shunt resistance Rsh losses attributed to the window layer were found to jointly contribute to the overall cell efficiency losses. A non-uniform pin-hole distribution, leading to Rsh loss, was found to be independent of the overall Cd1−xZnxS thickness distribution; thus the triple wavelength LBIC measurement was able to identify causes for the observed losses in both Voc and Rsh.

Reverse Bias Degradation in Shadowed Devices in TiO2 Dye-Sensitized Solar Cell Modules

ABSTRACTMismatched or shadowed individual cells in a module can operate in the Reverse Bias (RB) regime. Subjecting a dye solar cell (DSC) to an accelerated RB stress by forcing a constant current equal to 2-fold its ISC, produced significant alterations on the current-voltage (I-V) characteristics in RB with time and a severe loss of cell efficiency in 32h. We investigated and identified a key mechanism for RB charge transfer and degradation in DSCs. I-V characteristics in RB were found to be sensitive to the type of dye utilized and to TiCl4 substrate treatment.