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

Abstract

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.