Using MIS Thermally Stimulated Currents for Degradation Dependent Energetic Landscape Evaluation in Triple Cation Mixed Halide Perovskites

For perovskite solar cells (PSCs), despite the remarkable advancements in power conversion efficiency and environmental stability, degradation under operational conditions remains a barrier between research and commercialization. Understanding and monitoring the underlying physics of electronic band gap states during degradation as a result of ambient conditions is essential for further improvements in device stability. Here, advanced defect spectroscopy utilizing thermally stimulated currents (TSC) coupled to a metal‐insulator‐semiconductor (MIS) structure is used to determine the energetic landscape of band gap states in relevant state‐of‐the‐art triple cation mixed halide (TCMH) perovskite samples to demonstrate the capabilities of this method. MIS TSC is used to resolve the electrical effect of degradation induced by ambient conditions and natural illumination. Coupling these findings to optoelectronic and structural analysis of individual perovskite layers and functional PSCs, a correlation between material degradation, device performance and trap state evolution can be obtained. We find that with aging under ambient conditions and exposure to light, in TCMH the electron trap density is reduced, while the density of detected hole states increases. For this unexpected behavior, we propose a change of trap type and polarity during degradation.