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Engineering CuInGaSSe2 Surface Properties to Enhance Device Performance
Published online by Cambridge University Press: 01 February 2011
Abstract
The CuInGaSSe2/CdS heterostructure interface has a special effect on the performance of an important thin film photovoltaic device. The CdS buffer layer is essential to stabilize the performance of CuInGaSSe2 based devices. It adjusts the lattice mismatch at the absorber/window interface, repairs CuInGaSSe2 surface defects and protects it from air oxidation. Unfortunately, the CdS material has many environmental issues. This paper reports an alternate chemical approach to engineer the interface defects in CuInGaSSe2 and maximize its PV output. It describes a simple processing step to manipulate the defect density. This step could potentially reduce sensitivity to the ambience, widen the surface bandgap and replace the current hazardous processes used in state-of-the-art CuInGaSSe2 modules. Photocurrent and spectral response measurement in an electrolytic medium monitor the effects of surface modification, specific metal ions and time. The CuInGaSSe2 films respond easily to a number of external stimuli with either positive or negative changes in the electro-optic properties. Strong time dependence of the photocurrent suggests a dynamic equilibrium of point defects in the CuInGaSSe2 film. The results provide new insights into the effects of stoichiometry, deposition methods and oxide formation, on the defect chemistry. They also provide directions for reconfiguring the deep defects for enhanced device performance without the need for toxic etchants or buffer layers, and the environmental hazards associated with these steps.
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- Copyright © Materials Research Society 2004