ИСТИНА

Complex lead halides incorporating simultaneously a few univalent cations such as cesium (Cs+), methylammonoium (MA+) and formamidinium (FA+) represent highly promising materials for perovskite solar cells delivering record-high power conversion efficiencies. Unfortunately, these materials demonstrate insufficient stability, which limits their practical implementation; therefore, improving the photochemical and thermal stability of multication lead halide perovskites is an urgent task, which needs to be addressed to achieve sufficiently long operational lifetimes of perovskite solar cells which are required for their massive real-life applications. Herein, we present a comparative study of two azaadamantane-based molecular modifiers as stabilizing additives for Cs0.10MA0.15FA0.75PbI3 and Cs0.12FA0.88PbI3 perovskite formulations. An iodide of N-methylated 1,3,5,7-tetraazaadamantane known as urotropine (MAdI) showed a modest stabilizing effect reflected in a decreased amount of PbI2 formed as the decomposition product from Cs0.10MA0.15FA0.75PbI3 and suppressed light-induced crystallization of Cs0.12FA0.88PbI3. On the contrary, 4,6,10-trihydroxy-1,4,6,10-tetraazaadamantane hydrochloride (NAdCl) strongly enhanced the stability of both lead halide perovskites and prevented the formation of metallic lead Pb0 as a photolysis product. Different stabilizing effects caused by MAdI and NAdCl were related to their different localization within the perovskite films as evidenced by nanoscale infrared (IR) s-SNOM microscopy.