A molecular acceptor with absorption wavelength of >1400 nm for short-wavelength infrared organic photodetectors

Abstract

Short-wavelength infrared (SWIR) organic photodetectors (OPDs) hold significant promise in fields such as artificial intelligence, remote sensing, machine vision, medical imaging, etc. However, the development of SWIR OPDs remains hindered by the scarcity of ultra-narrow bandgap electron donors or acceptors. In this study, a novel small molecular acceptor BTQ-1, featuring an ultra-narrow bandgap and absorption extending up to 1569 nm, was designed for SWIR OPDs. BTQ-1 consists of a dithienothiophen[3,2-b]pyrrolobenzothiadiazole (BTP) core unit, two cyano-substituted alkoxythiophene π bridges, and two quinoidal 2-[4-oxonaphthalen-1(4H)-ylidene]malononitrile (QC) end groups. With an optical bandgap of 0.79 eV and peak absorption at 1009 nm, BTQ-1 demonstrates strong SWIR absorption due to intramolecular charge transfer and quinoidal resonance within its molecular structure. The use of BTQ-1 as an electron acceptor in OPD can achieve light detection at 500–1400 nm, with a detectivity at 940 nm up to 3.42 × 10⁹ Jones and a sustained detectivity of 4.30 × 10⁸ Jones at 1310 nm. This work provides a narrow bandgap electron acceptor with absorption extending beyond 1400 nm for SWIR OPDs.