Space-confined growth of high-quality CsBi 3 I 10 lead-free perovskite film for near-infrared photodetectors with high sensitivity and stability

As a lead-free perovskite, CsBi3I10 has attracted significant attention because of its high thermal tolerance and long electron diffusion length. Solution-processed high-performance CsBi3I10 perovskite devices, however, are hindered by the formation of a two-dimensional structure, which results in an extremely high surface roughness and many pinholes. In this paper, we reported a space-confined growth (SCG) method using a single-layer polystyrene (PS) sphere template to obtain high-smoothness, high-crystallinity, and dense CsBi3I10 perovskite films. Compared with traditionally spin-coated CsBi3I10 photodetectors (PDs), the metal-semiconductor-metal PDs made by SCG showed a higher photocurrent, a lower dark current, and a bigger on/off ratio. In addition, the photocurrent of our unencapsulated CsBi3I10 perovskite PDs was not attenuated under long-time illumination. In addition, when the device was stored in air for 30 d, its performance also showed no degradation, demonstrating ultra-high stability. Furthermore, the synthesis was free of antisolvents, such as chlorobenzene and toluene, which is beneficial for the environmentally friendly assembly of the devices. Our strategy opens up a new way to prepare high-quality lead-free perovskite, which may be useful for applications in light-emitting diodes and solar cells.