General Decomposition Pathway of Organic–Inorganic Hybrid Perovskites through an Intermediate Superstructure and its Suppression Mechanism

Organic–inorganic hybrid perovskites (OIHPs) have generated considerable excitement due to their promising photovoltaic performance. However, the commercialization of perovskite solar cells (PSCs) is still plagued by the structural degradation of the OIHPs. Here, the decomposition mechanism of OIHPs under electron beam irradiation is investigated via transmission electron microscopy, and a general decomposition pathway for both tetragonal CH3NH3PbI3 and cubic CH3NH3PbBr3 is uncovered through an intermediate superstructure state of CH3NH3PbX2.5, X = I, Br, with ordered vacancies into final lead halides. Such decomposition can be suppressed via carbon coating by stabilization of the perovskite structure framework. These findings reveal the general degradation pathway of OIHPs and suggest an effective strategy to suppress it, and the atomistic insight learnt may be useful for improving the stability of PSCs. A general decomposition pathway from tetragonal CH3NH3PbI3 and cubic CH3NH3PbBr3 to lead halides is revealed, through the formation of an intermediate superstructure CH3NH3PbX2.5 with ordered vacancies. A carbon coating is demonstrated to be effective in stabilizing the perovskite framework, and thus slowing down the decomposition.