Molecular Engineering of Hole-Selective Layer of TexSe1–x for High-Performance Short-Wave Infrared Photodetectors

Abstract

Short-wavelength infrared (SWIR) photodetectors are essential to human activities in military and civilian fields, including night vision, remote sensing, telecommunication, medical applications, safety monitoring, and mineral identification. Recently, the tellurium–selenium (Te_xSe_1–x) alloy has demonstrated considerable potential in infrared photodetection. However, the photodetectors still suffer from poor device performance. Herein, we present an interfacial engineering strategy to enhance carrier transport in the Te_xSe_1–x photodetector by utilizing a self-assembled monolayer (SAM) of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) as an interface layer between the Te_xSe_1–x active layer and the poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA) hole transport layer. Density functional theory calculations and in-depth XPS analysis illustrate the occurrence of charge transfer and the formation of P–Se bonds at the Te_xSe_1–x/SAM interface. This interfacial engineering approach leads to a more homogeneous surface potential, an increased built-in voltage, improved energy band alignment, and superior photoelectronic characteristics. The self-powered Te_xSe_1–x photodetector exhibits an external quantum efficiency (EQE) of 46% ± 1% at 980 nm and 19.7% ± 0.5% at 1320 nm. This makes the first demonstration of Te_xSe_1–x photodiode achieving a high responsivity of 0.49 A W^–1, along with a record total noise determined realistic detectivity $\left(D_2^{*}\right)$ of 7.69 × 10¹⁰ Jones (and 5.75 × 10¹¹ Jones when considering only shot noise) at 1319 nm, combined with an ultrafast response time of <547 ns (as measured under femtosecond pulsed laser illumination). Moreover, the photocurrent of this photodetector remains almost unchanged even after 30 days of storage.