Strain in\nHalide Perovskites and Solar Cell Stability:\nAccelerated Stress Tests under Bias Voltage

The lifespan of halide perovskite solar cells (PSCs)\nis currently\na major concern for the implementation and commercialization of the\ntechnology. Tensile and compressive strain alters the halide perovskite\n(HP) lattice under operando conditions, affecting PSC stability. However,\nthe mechanisms governing strain responses are still unknown. In this\nwork, we monitored the evolution of strain in PSCs during accelerated\nstability tests under continuous light irradiation and bias-voltage.\nAdditive engineering led to a compression of the HP lattice, improving\nPSC stability. The temporal evolution of the HP lattice, together\nwith the electrical response of devices employing modified and reference\nHP, was tracked by <i>in situ</i> X-ray diffraction, photoluminescence,\nand quasi <i>in situ</i> electrochemical impedance spectroscopy.\nOur results demonstrate a good correlation between lattice expansion\n(strain) and the device’s current decay and stability. Additionally,\nand contrary to the current understanding, we observed that lattice\ncompression in HP was not sufficient to ensure protection against\ndegradation.