Structure-Controlled Cyclopentadithiophene Derived Non-Fullerene Acceptors for Efficient Near-Infrared Organic Photodetectors

Abstract

High-performance near-infrared (NIR) organic photodetectors are still limited by insufficient absorption beyond 900 nm and the concomitant increase in dark current and noise. Here, we present organic photodetectors based on novel low-bandgap non-fullerene acceptors (NFAs), OC and SC, designed via a molecular strategy that introduces dithieno[3,2-b:2 ',3 '-d]pyran (DTP) and dithieno[3,2-b:2 ',3 '-d]thiopyran (DTTP) as central cores. The resulting PTB7-Th:OC organic photodiodes (OPDs) exhibit well-minimized dark-current densities (similar to 10-8 A cm-2) under a reverse bias of -2 V and maintain high spectral responsivities across the short-NIR region, reaching 0.4 A W-1 around 900 nm and remaining appreciable up to 1000 nm, leading to an excellent shot-noise-limited specific detectivity exhibiting 2.34 & times; 1012 Jones. Furthermore, the practical applicability of PTB7-Th:OC-based OPDs is demonstrated in a NIR photoplethysmogram sensor, which delivers stable and clearly resolved signals. Overall, this work highlights DTP/DTTP-based NFAs as promising materials for high-performance NIR-responsive OPDs and provides useful design guidelines for future NIR photodetection applications.