Effects of temperature-dependent burn-in decay on the performance of triple cation mixed halide perovskite solar cells

The understanding of the degradation mechanisms in perovskite solar cells (PSCs) is important as they tend to degrade faster under exposure to heat and light conditions. This paper examines the temperature-dependent degradation of solution processed triple-cation mixed halide PSCs (Cs0.05(FA0.95MA0.05)0.95Pb(I0.9Br0.05)3). The PSCs were subjected to temperatures between 30 and 60 °C for 3 h (180 min) to evaluate their current–voltage performance characteristics. Temperature-induced changes in the layer and interfacial structure were also elucidated by scanning electron microscopy (SEM). Our results show that thermally induced degradation leads gradually to the burn-in decay of photocurrent density, which results in a rapid reduction in power conversion efficiency. The SEM images reveal thermally induced delamination and microvoid formation between the layers. The underlying degradation in the solar cell performance characteristics is associated with the formation of these defects (interfacial cracks and microvoids) during the controlled heating of the mixed halide perovskite cells. The electrochemical impedance spectroscopy analysis of the PSCs suggests that the device charge transport resistance and the interfacial capacitance associated with charge accumulation at the interfaces both increase with extended exposure to light.