Open-Shell Conjugated Polymers Enable Photothermoelectric Conversion and Detection of Short-Wave Infrared Light.

Short-wave infrared (SWIR) light constitutes a significant yet underutilized portion of the solar spectrum, and efficient harvesting and detection of SWIR photons are increasingly required for emerging photonic and energy technologies. Here, we demonstrate SWIR energy harvesting and photodetection using an organic photothermoelectric (OPTE) device based on a proquinoidal diradicaloid-type conjugated polymer, PBBT2T-T, which exhibits broadband absorption extending from the visible to the SWIR region due to intrinsic free-charge carriers. After F4TCNQ doping, the OPTE device delivered an open-circuit voltage of 329.6 µV, a short-circuit current of 2.67 µA, and a maximum output power of 0.22 nW under >1000 nm illumination (50 mW cm-2). Furthermore, the device functions as an OPTE detector capable of sensing SWIR light beyond 1500 nm, achieving a responsivity of 0.0063 V W-1 and a detectivity of 8.4 × 105 Jones. Notably, this result successfully demonstrates SWIR photodetection based on the photothermoelectric effect for the first time. These findings establish OPTE conversion as a promising strategy for SWIR energy harvesting and photodetection, with strong potential to overcome the intrinsic limitations of conventional organic SWIR optoelectronic technologies.