High-performance thin-film photodetector based on lead-free perovskite CsBi 3 I 10 /C8-BTBT heterojunction

Abstract Lead-based perovskites have garnered widespread attention due to their excellent optoelectronic properties. However, despite the development of several lead-based perovskite photodetectors, issues related to material toxicity, air stability and device performance have hindered their wide application. Herein, we report a lead-free perovskite CsBi 3 I 10 /C8-BTBT heterojunction thin-film photodetector with remarkable on/off ratios and responsivity, which shows distinct advantages to the device among bismuth-based perovskite photodetectors. Based on one-step spin-coating method, we firstly prepared CsBi 3 I 10 thin films with high crystallinity, smooth surfaces, and strong light absorption capabilities by optimizing the process. Furthermore, the device performance was improved by constructing the CsBi 3 I 10 /C8-BTBT heterojunction, which is characterized by a type-II band alignment, significantly improving the crystallinity and light absorption. Under 642 nm illumination and a bias voltage of 1 V, the heterojunction photodetector achieved impressive performance, with a responsivity of 0.38 A W −1 , a detectivity of 3.25 × 10 12 Jones, and an on/off ratio of 4.61 × 10 4 . Compared with the single CsBi 3 I 10 film device, it has increased by 3.8-fold, 10.8-fold, and a 46-fold. Additionally, the device also exhibited fast response times of 7.5 ms (rise) and 12.7 ms (fall), excellent stability and pattern recognition imaging capabilities, thereby laying the foundation for the development of high-performance, lead-free perovskite heterojunction photodetectors.