Efficient Carrier Transport in 2D BiOSe/CsBiI Perovskite Heterojunction Enables Highly-Sensitive Broadband Photodetection.

2D BiOSe has recently garnered significant attention in the electronics and optoelectronics fields due to its remarkable photosensitivity, broad spectral absorption, and excellent long-term environmental stability. However, the development of integrated BiOSe photodetector with high performance and low-power consumption is limited by material synthesis method and the inherent high carrier concentration of BiOSe. Here, a type-I heterojunction is presented, comprising 2D BiOSe and lead-free bismuth perovskite CsBiI, for fast response and broadband detection. Through effective charge transfer and strong coupling effect at the interfaces of BiOSe and CsBiI, the response time is accelerated to 4.1 µs, and the detection range is expanded from ultraviolet to near-infrared spectral regions (365-1500 nm). The as-fabricated photodetector exhibits a responsivity of 48.63 AW and a detectivity of 1.22×10 Jones at 808 nm. Moreover, efficient modulation of the dominant photocurrent generation mechanism from photoconductive to photogating effect leads to sensitive response exceeding 10 AW for heterojunction-based photo field effect transistor (photo-FETs). Utilizing the large-scale growth of both BiOSe and CsBiI, the as-fabricated integrated photodetector array demonstrates outstanding homogeneity and stability of photo-response performance. The proposed 2D BiOSe/CsBiI perovskite heterojunction holds promising prospects for the future-generation photodetector arrays and integrated optoelectronic systems.