Isolate Utilization of Plasmonic Hot Holes in Optoelectronic Enhancement for Copper Iodide (CuI): A Cross-Investigation by Confocal Kelvin Probe Force Microscopy

Nonradiative decays of surface plasmon (SP) can generate photocarriers in femtosecond, and it therefore has been attracting widespread research attention in ultrafast optoelectronics. Taking advantage of the probe technique, Kelvin probe force microscopy (KPFM) can characterize the spatial distribution of hot carriers in nanoscale and thereby provide necessary analysis for device investigation and engineering. In this work, the behavior of plasmonic hot holes is demonstrated for Ag nanoparticles (NPs) based on the fabrication of CuI hole transport layers. The morphological, optical, and electronic properties of Ag NPs and CuI films are systematically investigated. With the confocal lasers of over- and sub-bandgap wavelength, reversed evolution trends of surface potentials are observed by KPFM, indicating the effective injection of hot holes into CuI valence band (VB). Cross-verification is also performed based on the fabrication of metal–semiconductor–metal (MSM) photodetectors, and the photoelectrical tests highly dovetail with the surface potential evolution. This research provides an important reference for the plasmonic photoelectronics in both device design and research methods.