Blocking thin-film nonuniformities: Photovoltaic self-healing

Abstract

An approach is developed to block the effects of lateral nonuniformities in thin-film semiconductor structures. The nonuniformity modulates the surface photovoltage distribution. When exposed to light and immersed in a proper electrolyte, this distribution will generate laterally nonuniform electrochemical reactions. Such treatments result in a nonuniform interfacial layer that balances the original nonuniformity. This approach has been implemented for CdTe/CdS photovoltaic devices, in which it improved the device efficiency from 1%–3% to 11%–12%.

Amorphous silicon/polyaniline heterojunction solar cells: Fermi levels and open-circuit voltages

“…It thus seems unlikely that the electrophoresis mechanism is correct since it fails to predict the observed difference between c-Si and a-Si:H. A second mechanism for limiting V OC might be lateral inhomogeneities in our polyaniline. An experiment on CdS/CdTe solar cells showed that blocking such inhomogeneities improved V OC and cell efficiency dramatically [16]. However, for the a-Si:H based n/i/PANI structures, we did not find saturation of V OC for the larger PANI conductivities, which seems to exclude this possibility.…”

Understanding Aniline Surface Treatment of CdTe

“…As observed by Roussillon et al [3], following a successful treatment, the CdTe surface changes to a light gray color. Sometimes, following certain treatment conditions, an organic film can be observed on the CdTe surface.…”

“…CdTe treatments generally involve oxidizing wet chemical etches, for example Br 2 /methanol (BM) and HNO 3 /H 3 PO 4 (NP), but these often tend to be reactive, corrosive and toxic, and care is required to prevent over-etching of the CdTe surface. Recently, a new surface treatment was reported by Roussillon et al [3], where CdTe/CdS structures where treated under illumination in red wine and in aqueous solutions based on aniline (see Figure 1a for structure). Following contacting, devices treated with these solutions showed significant improvements in performance, exceeding 11% conversion efficiency, compared to devices that had not received treatment.…”

“…Standard aqueous aniline baths are based on those of Roussillon et al [3], containing 0.1 M aniline, 0.01 M p-toluenesulfonic acid (p-TSA) and 1 M NaCl electrolyte at pH∼6.2. All baths were freshly prepared unless otherwise stated.…”

Numerical analysis of degradation kinetics in CdTe thin films

“…The other types of degradation in CdTe devices which arise from the hot spot runaway and surface nonuniformities were considered with a different approach elsewhere (e.g. thermal-electrical coupled model) and are not the subject of this study (Karpov, 2012;Karpov et al, 2013;Roussillon et al, 2004).…”