Understanding the thermal degradation mechanism of perovskite solar cells via dielectric and noise measurements.

Long term stability is a major obstacle to the success of perovskite solar cell (PSC) photovoltaic technology. PSC performance deteriorates significantly in the presence of humidity, oxygen, exposure to UV light and heat. Here the change in charge transport properties of PSC with temperature and the associated significant drop in device performance at high temperature have been investigated. The latter is shown to be primarily due to an increase in charge carrier recombination, which impacts the open-circuit voltage. To understand the pathway of temperature-induced degradation, low-frequency 1/f noise characteristics, and the capacitance-frequency, as well as capacitance-voltage characteristics, have been investigated under various conditions. The results show that at high operating temperature accumulation of ions and charge carriers at the interface increase the surface recombination. Aging experiment at different temperature shows high stability of PSCs up to temperature < 70 °C, but a drastic, irreversible degradation occurs at higher temperature (80 °C). Low-frequency 1/f noise study revealed that the magnitude of normalized noise in degraded perovskite solar cell is four orders of magnitude higher than the pristine device. This study shows the power of low-frequency noise measurement technique as a highly sensitive non-invasive tool to study the degradation mechanism of PSCs.