Investigations on lead free perovskites based thin films and their degradation for solar photovoltaic applications

Abstract

newline Perovskite solar cells have attracted substantial interest owing to its ability to achieve efficiencies gt20% within a few years of development. However, for any solar cell to become technologically viable, it has to achieve two additional milestones along with being highly efficient: i.e. means of industrial production and good operational stability. The former is mostly addressed by the private sector and industrially-oriented research institutes. Whereas understanding the degradation pathways and improving the stability of perovskite solar cells have become one of the important research topics in the field of emerging photovoltaic. The present thesis titled Investigations on lead-free perovskites based thin-films and their degradation for solar photovoltaic applications is also focussed on degradation study of CH3NH3PbI3 and CsSnI3 perovskite thin films exposed to different environmental conditions. Lead and lead-free perovskite thin films were fabricated in a controlled environment to study the degradation pathways using structural and optical characterizations. CsSnI3 transformed to Cs2SnI6 in presence of air is an environmentally stable material. It possesses a bandgap of 1.6 eV with high absorption coefficient thus suitable as an absorber material. To examine the effect of thickness and defect density of absorber material on the efficiency of the device, an ab-initio numerical simulation of lead and lead-free perovskite solar cell is performed using SCAPS-1D software. The influence of various types of hole transporting materials was compared to optimize the efficiency of the device. Lastly, the lead-free perovskite solar cell was fabricated using Cs2SnI6 as an absorber layer and P3HT as a hole transport layer. The device achieved an efficiency of 0.87% and almost retained its stability when exposed to air for 140 hours.