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

Aims: This work reports 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 the 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 the postannealing process instead of using the previous way that increased the annealing temperature. Methods: The CsPbBr3-CsPb2Br5 compound powder was deposited directly on the surface glass substrate by thermal evaporation to form the CsPbBrCsPbBr3-CsPb2Br5 compound thin film. The thin films were post-annealed at 150°C for 15 min to crystallize. The DMSO liquid was dropped on the substrate; the liquid would then evaporate completely, leading to the formation of DMSO steam during 150°C post-annealing. The DMSO steam would cover the thin film completely, assisting with crystallization. Finally, the gold electrodes were deposited on the surface of thin films with a conductive channel of 1 mm´ 100 mm. Results: Results showed the crystalline quality of the thin film after DMSO steam annealing to be greatly improved compared to that of the thin film without DMSO steam annealing. The energy gap was between 2.355 eV and 2.293 eV, which was similar to a previous report. In addition, under 405 nm excitation, the photocurrent of the thin film annealed in DMSO steam showed a rapid response (35 ms), good dependence of photocurrent on light radiation power, and 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 shown improved 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 was found to possess high crystalline quality and enhanced photoresponse performance, compared to thin film without DMSO steam annealing.