Large Orthorhombic Polyhedral CsPbBr3 Nanocrystals for Ultrasensitive Photodetectors with Type‐I Structures

Abstract Lead halide perovskite nanocrystals (LHPs) are emerging with enormous potential for high‐performance optoelectronics. Regrettably, most of the reported lead halide nanocrystal‐based photodetectors (LHP‐PDs) focus on six‐faceted hexahedron (cube/platelet) shapes and encounter issues of interface recombination of the photogenerated electron‐hole pairs and low carrier migration efficiency. Herein, a vertical heterojunction photodetector with type‐I band alignment based on high‐quality polyhedral orthorhombic CsPbBr 3 nanocrystals (NCs) is designed and realized. The results show that utilizing these rhombic dodecahedron CsPbBr 3 as photosensitive layers, the p‐Si/CsPbBr 3 device presents high responsivity ( R ) and detectability ( D *) values of 8.36 A W −1 and 9.33 × 10 13 Jones, a powerful weak light detection capability with an ultralow noise equivalent power ( NEP ) of 2.14 × 10 −15 W Hz −1/2 , and a fast response time of 90/162 µs . Meanwhile, based on theoretical density functional theory (DFT) and energy band analysis, it is shown that the recombination of photogenerated electron‐hole pairs can be significantly suppressed, and the spectral response of the PDs is almost contributed by photogenerated carriers in CsPbBr 3 . The work provides a new avenue for improving the performance of PDs based on large‐size orthorhombic polyhedral CsPbBr 3 NCs by morphological structure modulation and optimized band alignment engineering.