Mixed-dimensional self-assembly organic–inorganic perovskite microcrystals for stable and efficient photodetectors

Abstract

The instability of organic–inorganic perovskites in humid air is a serious bottleneck that restricts their practical applications in optoelectronics, although tremendous achievements have been made in organic–inorganic perovskite devices. Materials engineering is believed to be one of the most direct strategies to address this issue. Mixed-dimensional organic–inorganic perovskite microcrystals, which exhibit relatively good charge carrier transport owing to the limited grain boundaries and low defect densities compared to perovskite thin films, integrate the good humidity stability of two-dimensional (2D) and single-phase quasi-2D perovskites and the high photoresponse of 3D perovskites in an individual crystal, rendering them as excellent candidates for the development of high-performance photodetectors. Herein, the (C₆H₅CH₂CH₂NH₃, PEA)₂(CH₃NH₃, MA)_n−1Pb_nBr_3n+1 (n = 1, 3, 5, ∞) perovskite microcrystals were synthesized using an anti-solvent vapor-assisted method, and the optoelectronic properties of these microcrystals were investigated by fabricating photodetectors in a lateral configuration. The (PEA)₂(MA)₂Pb₃Br₁₀ and (PEA)₂(MA)₄Pb₅Br₁₆ perovskites proved to be mixed-dimensional microcrystals, respectively, which consist of the single phases of 2D (PEA)₂PbBr₄, quasi-2D perovskite, and 3D MAPbBr₃. The photodetectors based on the individual (PEA)₂(MA)₂Pb₃Br₁₀ and (PEA)₂(MA)₄Pb₅Br₁₆ perovskite microcrystals perform better than the (PEA)₂PbBr₄ microcrystal photodetector and exhibit higher humidity resistance than the MAPbBr₃ device. The best performances are achieved in the (PEA)₂(MA)₄Pb₅Br₁₆ microcrystal photodetector with a high responsivity of 182.63 A W⁻¹, detectivity of 2.51 × 10¹⁴ Jones, and gain of 5.58 × 10², which can detect an optical signal with an extremely low light power density of 2.47 nW cm⁻². Our results demonstrate that developing mixed-dimensional perovskite microcrystals is a promising way to construct highly efficient and stable photodetectors.