Photodegradation of Triple-Cation Perovskite Solar Cells: The Role of Spectrum and Bias Conditions

Despite promising power conversion efficiencies, a key barrier for the future commercialization of perovskite-based solar cells (PSCs) is their lack of stability when exposed to sunlight for extended periods. This work investigates the phenomenon of light-induced degradation in triple-cation PSCs held at a constant voltage near the maximum power point and exposed to different regions of the solar spectrum. This light-induced degradation is expected to exhibit a strong wavelength dependence with a significant performance deterioration caused by high-energy photons. The challenging wavelengths are found to span over the range 300-500 nm, while longer wavelength light is found to be the least harmful for a mixed-cation perovskite composition when tested for a period of 250 h. The analyses of perovskite layers undergoing light-induced degradation indicate that the performance deterioration is directly linked to the decomposition of the perovskite absorber into lead iodide. The decomposition occurring in the bulk of the absorber material generates trap states with activation energies of 0.26 and 0.42 eV, determined using thermally stimulated current measurements. Apart from the spectral dependence of the degradation, bias conditions-such as open-circuit, short-circuit, or maximum power point-are found to have pronounced effects on light stability. These findings allow identifying strategies to improve the lifetime of PSCs.