Salutary impact of spontaneous oxidation in CHNHSnI on CZTS-based solar cell.

From the time of discovery, CHNHSnI has been a promising candidate in photovoltaics due to its outstanding optoelectronic properties. However, stabilization was not easy to achieve in CHNHSnI-based solar cells. Because CHNHSnI was used as an absorber, its naturally-occurring self-doping property spontaneously modified band alignment, which increased carrier recombination and decreased the efficiency of solar cell gradually. In this paper, for the first time, we have presented detailed study on use of CHNHSnI as a hole transport layer in prototype solar cell having configuration: CHNHSnI/CZTS/CdS/ZnO/AZO, using SCAPS software. To understand the effect of spontaneous self-doping property of CHNHSnI on solar cell performance, the analysis of variation in solar cell performance parameters, band alignment conduction band, valance band, Fermi levels, charge density, current density, conductance, capacitance and recombination rate was performed as a function of increasing CHNHSnI carrier concentration. It was found that, when used as an hole transport layer, the inherent self-doping property of CHNHSnI became a helpful trait to increase hole extraction and spontaneously enhanced our device efficiency. Thus, the inherent self-doping property of CHNHSnI transformed from curse to boon when we leveraged CHNHSnI as an hole transport layer in our solar cell device.