Design of All-Fused-Ring Nonfullerene Acceptor for Highly Sensitive Self-Powered Near-Infrared Organic Photodetectors

Sensitive detection of near-infrared (NIR) light underpins many important applications in academia and industry. In contrast to inorganic counterparts, organic semiconductors exhibit favorable attributes including solution processability, tailorable spectral response, mechanical flexibility, and nontoxicity. However, nowadays NIR organic photodetectors (OPDs) suffer from the scarcity of narrow-bandgap organic materials, low NIR responsivity, and a large dark current. Herein, we developed a novel narrow-bandgap nonfullerene acceptor, PDTTYM, and fabricated four OPD devices based on PDTTYM matched with four different polymer donors, which exhibited remarkable responsivities approaching 0.5 A W–1 in the NIR region ranging from 890 to 910 nm. By adjusting the bulk-heterojunction layer thicknesses in four OPD devices, we optimized the dark current densities (Jds) and the external quantum efficiencies of devices to get the optimized devices. Furthermore, we use Mott–Schottky analysis to evaluate the charge doping densities and depletion widths of four devices, which may explain the different dark current characteristics of our OPDs. All four optimized OPDs exhibit large specific detectivities around 1012 Jones for the NIR spectral region ranging from 780 to 1050 nm, which is close to that of a conventional commercial Si-based photodetector.