High-Performance Near-Infrared Organic Photodetectors Enabled by Fabricating an Interdigital Heterojunction

Near-infrared organic photodetectors (NIR-OPDs) are of significant applications in optical communication, medical monitoring, and bioimaging, and have become a centerpiece of organic photodetector (OPD) research. To overcome the well-known challenge of high dark current in NIR-OPDs, researchers have investigated and introduced the sequential deposition method to prepare photosensitive layers of gradient heterojunction structure. However, this photosensitive layer suffers from the issue of insufficient exciton diffusion length, which in turn limits the photoresponse performance of devices. To address this issue, an interdigital heterojunction (IHJ) structure is designed, forming the adjustable large-area bicontinuous phase, and constructing rich donor/acceptor interfaces and straightforward carrier transport channels. In this structure, the film shows enhanced crystallinity, which effectively reduces the trap density and suppresses the dark current. In addition, efficient exciton dissociation and charge extraction along with suppressed charge complexation promote the enhanced photoresponse of IHJ devices. Consequently, the IHJ NIR-OPD achieves a high detectivity of 7.35 x 1013 Jones at 805 nm at -0.2 V, which is one of the highest values at 800-900 nm among reported NIR-OPDs. Further, the IHJ devices are successfully applied to arterial pulse monitoring and transmission-based bioimaging. This study provides new insights for realizing high-performance NIP-OPDs. The interdigital heterojunction structure is designed, forming a tunable large-area bicontinuous phase. The abundant donor/acceptor interfaces and direct carrier transport channels enhance the device photocurrent, while the enhanced film crystallinity effectively reduces the trap density and suppresses the dark current. Therefore, high-performance near-infrared organic photodetectors with enhanced detectivity are obtained.image