Salutary impact of spontaneous oxidation in CH3NH3SnI3 on CZTS-based solar cell

From the time of discovery, CH3NH3SnI3 has been a promising candidate in photovoltaics due to its outstanding optoelectronic properties. However, stabilization was not easy to achieve in CH3NH3SnI3-based solar cells. Because CH3NH3SnI3 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 CH3NH3SnI3 as a hole transport layer in prototype solar cell having configuration: CH3NH3SnI3/CZTS/CdS/ZnO/AZO, using SCAPS software. To understand the effect of spontaneous self-doping property of CH3NH3SnI3 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 CH3NH3SnI3 carrier concentration. It was found that, when used as an hole transport layer, the inherent self-doping property of CH3NH3SnI3 became a helpful trait to increase hole extraction and spontaneously enhanced our device efficiency. Thus, the inherent self-doping property of CH3NH3SnI3 transformed from curse to boon when we leveraged CH3NH3SnI3 as an hole transport layer in our solar cell device.