Hindered Amine Light Stabilizers Increase the Stability of Methylammonium Lead Iodide Perovskite Against Light and Oxygen

Methylammonium lead iodide perovskite (MAPI) is a promising material for highly efficient photovoltaic devices. However, it suffers from photooxidation, which imposes strict requirements for its protection from oxygen during processing and operation. A hindered amine light stabilizer (HALS) has been found to exert a stabilization effect on methylammonium iodide (MAI) and MAPI against photooxidation. The HALS prevents the degradation of MAI by inhibiting the oxidation of iodide to iodine. Chemical modification of HALS allows its incorporation in MAPI films, which extends the resistivity of MAPI against photodegradation in ambient air from a couple of hours to several days, while causing no significant changes in key properties, such as optical absorption and charge transport. These results represent an important advance in the stabilization of MAPI against decomposition and demonstrate for the first time that antioxidants improve the stability of MAPI.