A Narrow-Bandgap Fused-Ring Acceptor for Organic Short-Wavelength Infrared Imager

Organic short-wavelength infrared (SWIR) imaging is a promising technology for consumer electronics and a broad range of other applications. The bottleneck of organic SWIR imaging is the lack of electron acceptors with ultrasmall bandgaps. Herein, we develop ultrasmall-bandgap electron acceptors by cyclizing the exocyclic vinylene linkers of a typical acceptor-donor-acceptor (A-D-A) electron acceptor with tetrafluorobenzene moieties. This tetrafluorobenzene cyclization redshifts the absorption spectrum by 224 nm and reduces the trap density of states of the neat film by nearly one order of magnitude. The resulting organic photodetector exhibits a peak responsivity of 0.36 A W^-1, a noise current of 1.41 × 10^-11 A Hz^-1/2 at 1 kHz, a specific detectivity exceeding 10⁹ Jones at 1140 nm under -1 V bias, and a linear dynamic range of 82 dB. Monolithic integration of this organic photodetector with thin-film transistor arrays yields a 256 × 256 pixel imager capable of high-contrast SWIR imaging. This work establishes tetrafluorobenzene cyclization as a powerful molecular paradigm for ultrasmall bandgap organic semiconductors, paving the way for low-cost, heavy-metal-free SWIR imagers in consumer electronics.