High‐Sensitivity Organic Photodetector Based on Surface‐Concentrated Nonfused Ring Electron Acceptor

Abstract Organic photodetectors (OPDs) with high photodetection abilities are essential requirements for ubiquitous light‐sensing devices. This work presents a simple nonfused ring electron acceptor (NFREA) named “TPDC‐4F” having optical bandgap of 1.42 eV, being designed as an efficient OPD via thickness control and additive engineering of the photosensitive layer. The optimized photosensitive layer composed of poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PM6) donors and TPDC‐4F acceptors shows a dramatically suppressed dark current of 3.55 × 10⁻⁹ A cm⁻². Moreover, it shows improved photoelectric properties and fast charge transfer even though the photosensitive layer thickness is as large as 330 nm. OPDs based on the 330‐nm‐thick PM6:TPDC‐4F with 1‐chloronaphthalene additive exhibit a high specific detectivity (D*) of 1.27 × 10¹³ cm Hz^1/2 W⁻¹ at 800 nm and a linear dynamic range of 122 dB under a bias of −0.1 V. The device also exhibits fast rise and fall times of 6.81 and 5.41 µs, respectively. This work demonstrates that the NFREA‐based OPDs offer competitive device performance compared to those based on fused‐ring electron acceptors.