Semitransparent Near‐Infrared Organic Photodetectors: Flexible, Large‐Area, and Physical‐Vapor‐Deposited for Versatile Advanced Optical Applications

Abstract Organic photodetectors (OPDs) have experienced remarkable performance improvements over the past decade thanks to significant advancements in organic material synthesis and device architecture engineering. In this study, high‐performance near‐infrared (NIR) OPDs with versatile advanced properties, including large detection areas, mechanical flexibility, and high transparency are realized. By incorporating a thin photo‐absorbing layer, functional blocking layers with a large energy gap, and semitransparent electrodes, the OPDs achieve an average visible transmittance (AVT) of up to 53.4% and color rendering index (CRI) of up to 95 within the human vision photopic response window of 380–780 nm. Both the small (6.44 mm 2 ) and large (256 mm 2 ) detection‐area semitransparent OPDs demonstrate an impressive external quantum efficiency (EQE) of 34% and 36%, and specific detectivity ( D *) of 1.4 × 10 13 and 1.1 × 10 12 Jones, respectively, comparable to silicon‐based inorganic photodetectors. As application demonstrations, OPDs with rigid and flexible substrates are employed for NIR imaging and biosensing, respectively. Notably, the flexible semitransparent OPDs are utilized as signal receivers in conjunction with semitransparent NIR organic light‐emitting diodes (OLEDs) operating as signal producers, demonstrating the feasibility of invisible optical communication. These OPDs represent the best‐performing see‐through devices with flexibility, making them promising candidates for integratable, bio‐compatible, and invisible optical‐sensing applications.