Self‐Powered Cs₃Bi₂I₉/ZnO Heterojunction Photodetector with Dual‐Band Photoresponse

Abstract Cs 3 Bi 2 I 9 /ZnO heterostructures are constructed by the growth of Cs 3 Bi 2 I 9 layer onto the spin‐coated ZnO films by a modified antisolvent recrystallization method, a series of Cs 3 Bi 2 I 9 /ZnO heterojunction photodetectors (PDs) with varied growth times of Cs 3 Bi 2 I 9 layer are fabricated. The construction of Cs 3 Bi 2 I 9 /ZnO heterojunction contributes to their improved photoelectric performance compared to ZnO‐based PD, and the Cs 3 Bi 2 I 9 layer thickness plays an important role in tuning the photoelectric performance of these PDs. At 405 nm and 0 V bias, the optimized 6‐Cs 3 Bi 2 I 9 /ZnO PD generates a high photocurrent of −3.03 µA, a medium on/off ratio of 144.3, and a short response time of 16.4 ms/16.8 ms. It also exhibits superior dual‐band self‐powered photoresponse with two responsivity and detectivity peaks at 380 nm in the UV region and at 430 nm in the visible light region. At 380 nm, this PD presents the highest responsivity of 33.2 mA W −1 and detectivity of 1.07 × 10 10 Jones. It is believed that the optimized growth of the Cs 3 Bi 2 I 9 layer generates a depletion layer with suitable thickness near the interface, and the as‐promoted charge‐carrier separation and transport result in improved self‐powered properties. The rational construction of perovskite‐based heterojunction has proved as an efficient way to achieve self‐powered photodetection.