A laminar MAPbBr3/MAPbBr3−xIx graded heterojunction single crystal for enhancing charge extraction and optoelectronic performance

Abstract

Halide perovskite single crystals (SCs) have recently been regarded as a promising candidate in optoelectronic devices by virtue of their remarkable intrinsic properties. Herein, a laminar MAPbBr₃/MAPbBr_3−xI_x (MA = CH₃NH₃⁺) graded heterojunction single crystal (GHSC) with a thickness of about 11 μm and an area of 4 × 5 mm has been synthesized via a space-limited inverse temperature crystallization growth method and a gaseous halide exchange process in sequence. Compared to the pristine MAPbBr₃ SC, such a MAPbBr₃/MAPbBr_3−xI_x GHSC possesses graded valence band alignment via a halide gradient distribution, which significantly enhances the hole extraction and accelerates carrier transport, leading to a high-performance perovskite SC photodetector with an improved external quantum efficiency of ≈170% at −2 V and an impressively rapid response speed of 0.56 μs. Our results provide a promising strategy to solve the carrier extraction obstacle and suppress recombination loss, which opens potential optoelectronic applications of laminar heterojunction SCs.