Low-Pressure Annealing and Surface Passivation of Self-Powered Wide-Bandgap CsPbCl₃ Nanostructure-Based Ultraviolet Photodetectors

The all-inorganic wide-bandgap CsPbCl3 perovskite is drawing increasing attention in the ultraviolet detection field due to its salient optoelectronic property and ultraviolet durability. However, the abundant intrinsic defects in polycrystalline CsPbCl3 nanofilms limit the UV detection performance of self-powered CsPbCl3 photodetectors. In this study, an efficient low-pressure annealing technique and a 4-chlorobenzoic acid (ClBA) modification strategy are proposed to suppress both the bulk and surface defects of evaporated CsPbCl3 nanofilms. It is found that low-pressure annealing can effectively ameliorate the crystallization dynamics of the CsPbCl3 nanocrystal, yielding a more homogeneous film with higher crystallinity and UV absorption capability as well as larger grain sizes and lower trap density. These are favorable for the photoelectric conversion process, thus contributing to a much enhanced UV detection performance. The multifunctional ClBA is further introduced to passivate the surface defects of the CsPbCl3 nanofilm. The electron-accepting end group of carboxyl in ClBA can effectively coordinate with the positively charged Pb2+, helping to suppress the Cl– vacancy defect and trap-assisted nonradiative carrier recombination. The ClBA passivation can also alleviate the interfacial energy barrier and enhance the charge transfer driving force, which is beneficial for improving the sensitivity and reducing the dark current level of the device. The best-performing photodetector achieves an excellent on/off ratio of 1.33 × 106, a responsivity R of 0.26 A/W, and a detectivity D* of 1.14 × 1013 Jones at 0 V bias, more superior than those of the previously reported self-powered CsPbCl3 counterparts. Additionally, our photodetector exhibits salient operational and ambient stability, conducive to their practical applications.