Partial Charge Transfer Complexes for Highly Efficient 2 µm Light Detection

ABSTRACT Achieving femtowatt sensitivity at room temperature remains an intractable challenge for organic shortwave infrared (SWIR) photodetectors (PDs), constraining their deployment in cutting‐edge imaging and sensing modalities. The inherent deficiencies of contemporary organic SWIR PDs, including curtailed spectral absorption (> 1.0 µm), diminished external quantum efficiency ( EQE ), and suboptimal detectivity ( D *), are inextricably tethered to trap‐induced non‐radiative recombination in narrow‐bandgap organic semiconductors. To surmount these limitations, we employ the prototypical organic partial charge transfer (PCT) complex bis–1,3–dithiole–tetrachloro–1,4–benzoquinone (BT–TCBQ), which leverages partial charge localization and low‐energy (< 0.7 eV) intermolecular electronic transitions. In this system, electrostatically tunable deep trap states (enabled by partial charge localization) amplify photo‐gating‐driven gain, while low‐energy photoactivated ionic donor‐acceptor pairs establish delocalized conduction pathways that suppress carrier scattering and Johnson‐Nyquist noise. This synergistic mechanism enables room temperature, electrostatically gate‐tunable operation with an EQE of ∼10 3 %, D * of ∼10 11 Jones, and a 135 ms response at 2.0 µm under a low bias of 0.1 V. Our innovative strategic deployment of PCT complexes epitomizes a significant advance in monolithically organic SWIR optoelectronics, obviating the reliance on hybrid architectures while rivaling the performance of state‐of‐the‐art inorganic counterparts.