Near-Infrared Organic Photodetectors with Spectral Response over 1200 nm Adopting a Thieno[3,4- c]thiadiazole-Based Acceptor

The nonclassical ten-pi-electron 5,5-fused thieno[3,4-c]thiadiazole (TTD) unit is an excellent building block for constructing sub-silicon-band gap organic semiconductors. However, no small molecule acceptor (SMA) materials based on TTD have been reported despite the fact that high-sensitivity near-infrared organic photodetectors (OPDs) are generally achieved by using SMAs. In this work, we report a TTD-based narrow band gap (0.95 eV) SMA material TTD(DTC-2FIC)₂ with strong near-infrared absorption. Employing PTB7-Th as a donor, OPDs based on TTD(DTC-2FIC)₂ exhibit an optimized responsivity of 0.095 (±0.007) A W^-1 at 1100 nm and sustain a decent responsivity of 0.074 (±0.008) A W^-1 at 1200 nm. Moreover, a good specific detectivity over 1 × 10¹¹ Jones is achieved at a wavelength of 1200 nm. Detailed characterizations imply that the performance of TTD(DTC-2FIC)₂-based OPDs may be substantially improved by choosing lower-mixing donors with shallower energy levels. This work demonstrates that SMAs incorporating TTD as the core unit hold promise for constructing high-sensitivity sub-silicon-band gap OPDs.