Structural investigation of co-evaporated methyl ammonium lead halide perovskite films during growth and thermal decomposition using different PbX2 (X = I, Cl) precursors

While the progress in device development of perovskite solar cells is rapidly evolving, details of the film formation and the interplay of processing parameters, structural and compositional properties of deposited phases and their stability are still under dispute. Here we present a detailed structural analysis of methylammonium lead halide (I, Cl) films by in situ X-ray diffraction during their growth and thermal recrystallization up to their decomposition. MAPbI3 films grown by co-evaporating MAI and PbI2 are compared to MAPbI3(Cl) films derived from an evaporation route using MAI and PbCl2 precursors. The main differences observed between the two routes are varying crystal structures at room temperature and differently limited process windows, but similar overall growth, recrystallization and decomposition features. The preferential orientation of the pure MAPbI3 is shown to depend on the applied molar precursor flux ratio and can additionally be modified by thermal annealing.