Self-assembled monolayer engineering improves 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 PPD 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 improved the response speed of the PPDs with the tunneling hole transporting properties and enhanced built-in potential with the induced interface dipole. In comparison to the PTAA based PPDs, the dark current level of (4-(7H-dibenzo[c,g]carbazol-7-yl)butyl) phosphonic acid (4PADCB) modified devices was reduced to 1.44 × 10⁻⁹ A cm⁻², the response rise/fall time was optimized from 901 ns/1.89 μs to 546/334 ns (both with an effective area of 6 mm²), and they exhibited a peak specific detectivity of 1.67 × 10¹³ Jones and high operational stability. These devices have been demonstrated as signal receivers in optical communication systems, presenting potential for application in light-fidelity (LiFi) networks.