Current–voltage characteristics of fully solution processed high performance CuIn(S,Se)2 solar cells: Crossover and red kink

• We report crossover and red kink behaviors of CuIn(S,Se)2 thin film solar cells with solution processed silver nanowire composite window (SNCW) layer.
• The distortions disappear during white-light illumination but gradually re-appear after turning off light.
• The illumination-dependent state of the acceptor-like defects at CdS/SNCW leads to the appearance and disappearance of the crossover and red kink.

We recently reported the successful replacement of both sputtered intrinsic zinc oxide (i-ZnO) and sputtered indium tin oxide (ITO) window layers by a solution processed silver nanowire composite window (SNCW) layer for fully solution processed high performance CuIn(S,Se)2 (CISS) thin film solar cells without any sacrifices in photovoltaic device performance. Here, we report the current density–voltage (J–V) characteristics of the fully solution processed CISS thin film solar cells with the SNCW layer under dark conditions, and under white and filtered red-light illumination. While control devices with sputtered conductive metal oxide window layers do not show J–V distortion, devices with the SNCW exhibit both crossover and red kink behaviors, which disappear during white-light illumination but gradually re-appear after turning off light. We propose the following model to explain the above observations. Acceptor-like defects at the CdS/SNCW interface become negatively charged by capturing electrons under dark conditions, but are neutralized by capturing photo-generated holes from the CdS valence band under white-light illumination. The illumination dependent state of the acceptor-like defects leads to the appearance and disappearance of the crossover and red kink from the J–V curves.