Self-Assembled Monolayer Engineering Facilitates the Sensitivity and Response Speed of High-Performance Perovskite Photodetectors

Abstract

Perovskite photodetectors (PPDs) have attracted significant attention due to their favorable optoelectronic properties and cost effectiveness. In recent years, self-assembled monolayers (SAMs) have been demonstrated to be effective as hole transport materials for photovoltaic devices to boost both efficiency and stability. Nevertheless, research on SAM-based interface engineering to optimize the photodetection is still rarely reported. In this study, by choosing different SAMs to replace the traditional poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) hole transport layer (HTL) for PPDs fabrication, we find that the dark current level is more determined by the highest occupied molecular orbital (HOMO) level of HTLs, rather than the crystallinity of perovskite layers. Moreover, the SAM HTLs significantly facilitate the response speed of the PPDs with the tunneling hole transporting properties and enhanced built-in potential with the induced interface dipole. In the comparison to the PTAA based PPDs, (4-(7H-dibenzo[c,g]carbazol-7-yl)butyl) phosphonic acid (4PADCB) modified devices reduce the dark current level to 1.44×10-9 A/cm², optimize the response rise/fall time from 901 ns/1.89 μs to 546/334 ns (both with effective area 6 mm²), and exhibit a peak specific detectivity of 1.67×1013 Jones and high operational stability. This device has been demonstrated as a signal receiver in an optical communication system, presenting potential in the light-fidelity (LiFi) networks.