Deuterating Narrow-Bandgap Organic Semiconductors for Sensitive Short-Wave Infrared Photodetection

Organic semiconductors exhibit significant potential for next-generation optoelectronic technologies owing to their structural tunability and solution processability; nevertheless, as their bandgap decreases, the nonradiative recombination for either exciton or photogenerated charge-carriers increases, limiting short-wave infrared (SWIR) photoresponse, as governed by energy gap law. Here, a deuteration strategy is employed to universally reduce the nonradiative decay pathways of SWIR organic semiconductors, enhancing photodetector sensitivity. Compared to protonated L4, the rational deuterated molecule (BT-12D) maintains SWIR photoresponse to ∼1.7 µm and exhibits lower stretching vibrational frequency (2350 cm^-1 vs. 3063 cm^-1), resulting in reduced recombination and 40% increase in specific detectivity (D^*) at 1.3 µm for PDPPDTP: BT-12D-based organic photodetectors (OPDs). Likewise, deuterated L2-eC9-10D-based OPDs blending with PTB7-Th exhibit 14% higher D^* (1.24 × 10¹² Jones at 1.2 µm) and faster rise/fall time (1.0/1.2 µs) than protonated devices (1.09 × 10¹² Jones; 1.6/1.7 µs). The optimized D^* of deuterated OPDs is comparable to and even better than those of commercial detectors at 0.9-1.2 µm, while the corresponding response time is the fastest value reported for SWIR OPDs. These results highlight the broad applicability of deuteration as an effective strategy to suppress nonradiative decay pathways in SWIR organic semiconductors, unlocking new opportunities for sensitive SWIR optoelectronics.