Low-temperature process for self-powered lead-free Cs2AgBiBr6 perovskite photodetector with high detectivity

In recent years, solution-processed lead halide perovskites have obtained great achievements in the field of optoelectronic devices. However, the instability and the toxicity of lead halide materials limit their commercial development. As a kind of lead-free perovskite, bismuth (Bi)-based double perovskite materials have become a research hot spot due to their high thermal stability and non-toxicity. Unfortunately, in the current preparation process, the solution-processed, high-quality Bi-based double perovskites need to suffer high post-treatment temperature, which seriously affects the interfaces between the perovskite/transport layer and is not friendly to the flexibility. Herein, by optimizing the DMF content in the Cs2AgBiBr6 precursor solution and spin coating speed, we obtained the optimal performance of the control device. On this basis, by adding ionic liquid to the optimal Cs2AgBiBr6 perovskite precursor, we greatly reduced the fabrication temperature of the Cs2AgBiBr6 from 285 to 150 °C, improved the stability of the device and the high-performance, flexible Cs2AgBiBr6 perovskite photodetectors (PDs) were fabricated at first. Through optimization, our low-temperature prepared Cs2AgBiBr6 perovskite PD showed high device performance with the switching ratio of 1.66 × 104, the linear dynamic range of 100 dB, the detectivity of up to 1.87 × 1012 Jones, and our flexible Cs2AgBiBr6 perovskite PDs also achieved the detectivity up to 8.04 × 1011 Jones with good flexible stability. This work provides a facile way to fabricate lead-free perovskites at low temperature.