Strain in Halide Perovskites and Solar Cell Stability: Accelerated Stress Tests under Bias Voltage

The lifespan of halide perovskite solar cells (PSCs) is currently a major concern for the implementation and commercialization of the technology. Tensile and compressive strain alters the halide perovskite (HP) lattice under operando conditions, affecting PSC stability. However, the mechanisms governing strain responses are still unknown. In this work, we monitored the evolution of strain in PSCs during accelerated stability tests under continuous light irradiation and bias-voltage. Additive engineering led to a compression of the HP lattice, improving PSC stability. The temporal evolution of the HP lattice, together with the electrical response of devices employing modified and reference HP, was tracked by in situ X-ray diffraction, photoluminescence, and quasi in situ electrochemical impedance spectroscopy. Our results demonstrate a good correlation between lattice expansion (strain) and the device's current decay and stability. Additionally, and contrary to the current understanding, we observed that lattice compression in HP was not sufficient to ensure protection against degradation.