Toward Highly Thermal Stable Perovskite Solar Cells by Rational Design of Interfacial Layer

Highlights•Degradation of perovskite films on different substrates were studied•The chemical and mechanical deterioration of perovskite films are distinguished•Thermal-induced stress within PVSCs was eased by a soft and thick interfacial layer•PVSCs with optimized interfacial layers showed superior thermal stabilitySummaryHeat is crucial to the long-term stability of perovskite solar cells (PVSCs). Herein, thermal stability of PVSCs based on metal oxide (MO) and polymer (P) was investigated. Firstly, chemical decomposition behavior of perovskite films was characterized and analyzed, revealing that chemically active MO would accelerate the decomposition of methylamine lead iodide (MAPbI3). Secondly, thermal-induced stress, resulting from the mismatched thermal expansion coefficients of different layers of PVSCs, and its effect on the mechanical stability of perovskite films were studied. Combining experiment and simulation, we conclude that "soft" (low modulus) and thick (>20 nm) interfacial layers offer better relaxation of thermal-induced stress. As a result, PVSCs employing thick polymer interfacial layer offer a remarkably improved thermal stability. This work offers not only the degradation insight of perovskite films on different substrates but also the path toward highly thermal stable PVSCs by rational design of interfacial layers.Graphical abstract