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High Versatility and Stability of Mechanochemically Synthesized Halide Perovskite Powders for Optoelectronic Devices.

We show that mechanochemically synthesized halide perovskite powders from a ball milling approach can be employed to fabricate a variety of lead halide perovskites with exceptional intrinsic stability. Our MAPbI3 powder exhibits higher thermal stability than conventionally processed thin-films, without degradation after more than two and a half years of storage and only negligible degradation after heat treatment at 220°C for 14 hours. We further show facile recovery strategies of non-phase-pure powders by simple re-milling or mild heat treatment. Moreover, we demonstrate the mechanochemical synthesis of phase-pure mixed perovskite powders such as (Cs0.05FA0.95PbI3)0.85(MAPbBr3)0.15 from either the individual metal and organic halides, or from readily prepared ternary perovskites, regardless of the precursor phase purity. Adding KI to the milling process successfully passivated the powders. We also succeeded in preparing a precursor solution on the basis of the powders and obtained uniform thin films from spin-coating this solution. This knowledge was used for efficient solar cells. We find the KI passivation remains in the devices, leading to improved performance and significantly reduced hysteresis. Our work thus demonstrates the potential of mechanochemically synthesized halide perovskite powders for long-time storage and upscaling, further paving the way towards commercialization of perovskite based optoelectronic devices.