Inverse Growth of Large Grain Size and Stable Inorganic Perovskite Micro-Nanowire Photodetectors.

Control of the forward and inverse reactions between perovskites and precursor materials is key to attaining high quality perovskite materials. Many techniques focus on synthesizing nanostructured CsPbX3 materials (e.g., nanowires) via a forward reaction (CsX + PbX2 → CsPbX3). However, lower solubility of inorganic perovskites and complex phase transition make it difficult to realize the precise control of composition and the length of nanowires using the conventional forward approach. Herein, we report a self-assembly inverse growth of CsPbBr3 micro-nanowires (MWs) (CsPb2Br5 → CsPbBr3 + PbBr2 ↑) by controlling phase transition from CsPb2Br5 to CsPbBr3. Two-dimensional (2D) structure of CsPb2Br5 serves as nucleation sites to induce the initial CsPbBr3 MW growth. Also, phase transition allows crystal rearrangement and slows down the crystal growth, which facilitates the MW growth of CsPbBr3 crystals along the 2D planes of CsPb2Br5. A CsPbBr3 MW photodetector constructed based on the inverse growth shows a high responsivity of 6.44 A W-1 and detectivity of ~1012 Jones. Larger grain size, high crystallinity and bigger thickness can effectively alleviate the decomposition/degradation of perovskites, which leads to storage stability over 60 days in moisture (45% relative humidity) and operational stability over 3000 min under illumination (400 nm, ~20.06 mW cm-2).