Polymer‐Assisted Phase Stable γ‐CsPbI3 Perovskite Film for Self‐Powered and Ultrafast Photodiodes

Abstract Lead‐halide perovskite materials have emerged as promising alternatives for optoelectronic applications due to their low‐cost, easily tunable bandgaps, and facile solution‐processability. Despite all their exciting merits, perovskite materials are currently suffering the stability issues, such as moisture and oxygen‐induced rapid degradation and phase transition. In this work, γ phase CsPbI 3 perovskite thin films with compact grain boundaries and improved ambient stability are successfully developed via introducing poly‐2‐ethyl‐2‐oxazoline (PEOXA) polymer through an effective bonding between CO double bond in PEOXA with perovskite. The optimized photodetectors with the γ‐CsPbI 3 :5%PEOXA active thickness as thin as 30 nm have a totally excellent performance with a responsivity of 0.16 A W −1 , high detectivity of 2.73 × 10 12 Jones, linear dynamic range of over 125 dB, and ultrafast rise/decay time of 13.9/12.7 µs. Moreover, the as‐constructed photodetectors have shown a high stability when maintained under ambient conditions. This work provides new insights for the development of highly stable and efficient perovskite‐based optoelectronics.