Ultrasonically sprayed Cs3Bi2I9 thin film based self-powered photodetector

In the present work, we report lead-free, all-inorganic, Cs3Bi2I9 perovskite-inspired films developed by ultrasonic spray deposition technique at various substrate temperatures which demonstrate promising photodetection properties without any external bias or power consumption. Uniform films of excellent adhesion to the substrate deposited from 150 to 400 °C were analyzed in detail using structural, morphological, optical and electrical characterization techniques. Highly crystalline films with well-packed grains were readily obtained below 325 °C substrate temperature. In addition, the degradation of the films during the growth at higher substrate temperatures was different from the normal decomposition of Cs3Bi2I9 due to post-deposition treatments. The thin films showed direct band gaps in the range of 1.8–2.1 eV with absorption coefficients in the order of ∼104 cm−1. Photocurrent in the nanoampere range was observed in all the phase-pure films under illumination by a 50 W halogen lamp. Moreover, the thin films were chemically stable even after rapid thermal processing up to 500 °C. Furthermore, self-powered photodetection using Ag/FTO/Cs3Bi2I9/C-Ag heterostructure is demonstrated under AM1.5 radiation as well as 532 and 405 nm laser illuminations. The highest responsivity and detectivity obtained for the Cs3Bi2I9-based photodetector were 0.0051 mAW−1 and 5.93 × 108 Jones (405 nm, 50 mW), respectively. Our investigations suggest that the spray deposited Cs3Bi2I9 films are promising for self-powered devices, especially in blue light detectors.