Reversible and irreversible degradation of perovskite solar cells

Abstract

The perovskite solar cells (PSCs) comfortably placed close to the top of record power conversion efficiency chart for lab scale solar cells is not sold in the market. Yes, this statement can be a dictionary example for the word 'oxymoron'. Even with improving efficiencies recorded every now and then and with good material properties for a good solar cell, the PSCs are not commercialized due to their instability in performance. PSCs often show an irreversible degradation under long term continuous illumination. However, in real life solar cells naturally undergo light dark cycling over day night periods. Therefore, in this work we have systematically investigated PSCs’ behavior through such light dark cycling. It is observed when the cell temperature stays constant under light, the efficiency of PSCs slightly decreases during daytime but fully recovers after a night’s rest in dark. In contrast, if the cell experiences temperature variation under light, which is more realistic for outdoor conditions, even after rest in night, the efficiency does not fully recover. To explain these observations, a hypothesis relating the ionic defect generation and migration to the change of built in field across light dark cycling is proposed. This work suggests it’s vital to avoid irreversible PSC degradation by undermining defects formation and migration.