Synergistic Benzohydrazide (BH) and Zinc Bromide (ZnBr2) Doping for α-CsPbI3 Perovskite Films and Photodetectors via One-Step Co-evaporation

All-inorganic CsPbI3 perovskite is a promising optoelectronic material; however, its device performance is impeded by phase instability and defect-mediated nonradiative recombination. Here, we present a synergistic co-doping strategy employing benzohydrazide (BH) and zinc bromide (ZnBr2) to concurrently address these challenges. High-quality α-phase CsPbI3 thin films are fabricated via a controllable one-step thermal co-evaporation process followed by low-temperature (70 °C) annealing. The BH molecule effectively passivates undercoordinated Pb2+ defects, while Zn2+ substitution at the B-site contracts the lattice, enhancing phase stability. Optimal co-doping (3.3 wt % BH, 23.0 mol % ZnBr2) yields dense, pinhole-free films with refined grains (∼18.4 nm), a low trap density of 1.62 × 1016 cm–3, and a prolonged carrier lifetime of 34.3 ns. Planar photodetectors based on the optimal film exhibit a remarkable responsivity of 2456 A W–1 at 720 nm, a specific detectivity of ∼1013 Jones, and fast response times (∼0.2 ms), outperforming most reported CsPbI3-based devices. This work demonstrates an effective materials-engineering approach for high-performance, stable perovskite optoelectronics.