Electron Acceptors Based on Resonant N─B←N Unit with Improved Exciton Dissociation for High-Performance Short-Wavelength Infrared Organic Photodetectors

Abstract

Device performance of photodiode-type short-wavelength infrared (SWIR) organic photodetectors (OPDs) is largely limited by poor exciton dissociation. In this work, we reported that downshifted highest occupied molecular orbital energy level (E_HOMO) and increased electrostatic potential (ESP) of electron acceptor lead to improved exciton dissociation and consequently enhanced SWIR OPD device performance. Tetramers of thiophene-fused 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (TF-BODIPY) unit represent a new kind of electron acceptors with SWIR photoresponse. By endcapping the TF-BODIPY tetramer with electron-deficient pentafluorophenyl groups, we downshift the E_HOMO of the electron acceptor by 0.06 eV and increase the ESP of the electron acceptor by 89 meV. As a result, the OPD devices of the electron acceptor exhibit SWIR photoresponse in the wavelength range of 0.3–1.3 µm with a maximum specific detectivity (D*) of 1.04 × 10¹² Jones and a responsivity (R) of 0.16 A W⁻¹ at 1.12 µm. This performance is among the highest reported for SWIR OPDs.