Organic Semiconductors with Halogenated Quinoid Terminals for Sensitive Short-Wave Infrared Detection and Imaging.

Abstract

Short-wave infrared (SWIR) detection and imaging is vital for optoelectronics, and solution-processed organic semiconductors pave the way for developing large-area, cost-effective SWIR sensor arrays compatible with readout integrated circuits through facile pattern-free processing. However, limited by the energy gap law, molecular skeleton vibrations, especially high-frequency stretching modes like C─H bonds, induce accelerated non-radiative decay in SWIR molecules, making the performance of SWIR organic photodetectors (OPDs), particularly in the long-wavelength region, still lag behind that of commercial inorganic counterparts. Here we develop an efficient molecular engineering strategy to construct vibration-suppressed SWIR molecules by employing halogenated quinoid terminals. Relative to their analogs with H atoms, halogenated semiconductors show attenuated exciton-vibration coupling, decreased conformation and energy disorder, as well as enhanced intramolecular charge transfer, resulting in nearly doubled exciton lifetimes and reduced energy disorder from 103 to 66-83 meV, accompanied by 0.1-0.15 eV optical bandgap narrowing. The optimized SWIR OPDs achieve broadband photoresponse (0.3-1.6 µm) and high specific detectivities up to 2.11 × 10¹¹ Jones at 1.03 µm, overwhelming all reported OPDs with >1.4 µm response and comparable to Ge photodetectors in 0.9-1.4 µm range. Furthermore, we demonstrate an advanced active-matrix OPD-based SWIR imaging system prototype, showcasing applicability in diverse SWIR scenarios.