A 405 nm Photodetector Based on the CsPbBr3-CsPb2Br5 Compound Thin Film

Abstract

Aims: This work reported a 405 nm photodetector based on the thermal evaporated CsPbBr3-CsPb2Br5 compound thin film. Background: The post-annealing process of the CsPbBr3-CsPb2Br5 compound thin film prepared by thermal evaporation method has been improved in this work. To enhance the crystallization and photoresponse properties of the thin films, dimethyl sulfoxide (DMSO) steam was used in post-annealing process, instead of using the previous way that increased the annealing temperature. Methods: The CsPbBr3-CsPb2Br5 compound powder was deposited directly on surface glass substrate by thermal evaporation to form CsPbBr3-CsPb2Br5 compound thin film. The thin films were post-annealed at 150 oC for 15 min to crystallize. The DMSO liquid was dropped on the substrate, and then the liquid would be evaporated completely to become DMSO steam during 150 oC post-annealing. The DMSO steam would cover the thin film completely to help the crystallization. Finally, the gold electrodes were deposited on surface of thin films with a conductive channel of 1 mm * 100 µm. Result: Results showed that the crystalline quality of the thin film after DMSO steam annealing was greatly improved compared with that of thin film without DMSO steam annealing. The energy gap was between 2.355 eV and 2.293 eV, which was similar to the previous report. In addition, under 405 nm excitation, the photocurrent of the thin film annealed in DMSO steam showed the rapid response (35 ms), good light radiation power dependence of the photocurrent and the improved responsivity. Especially, the responsivity at 3 V bias of the thin film annealed in DMSO steam increased to 1.5 times that of the thin film without DMSO steam annealing and even 4.5 times that of as-deposited film. Conclusion: A 405 nm photodetector based on the thermal evaporated CsPbBr3-CsPb2Br5 compound thin film was prepared successfully. The newest report has improved the preparation process of CsPbBr3-CsPb2Br5 compound thin films, where low annealing temperature with the DMSO steam assisted post-annealing process was used. The thin film annealed in DMSO steam possesses high crystalline quality and enhanced photoresponse performances, compared with thin film without DMSO steam annealing.