Aggregation‐Induced Enhancement of Deep‐UV Response in Indoloindole‐Based Organic Photodetectors

Abstract Organic photodetectors operating in the deep‐ultraviolet region are crucial for environmental monitoring, biomedical imaging, and sterilization systems. Two novel indolo[2,3‐ b ]indole derivatives with systematic alkyl chain variation: 5,6‐didodecyl‐5,6‐dihydroindolo[2,3‐ b ]indole ( ID23b‐C12 ) and 5,6‐dihexadecyl‐5,6‐dihydroindolo[2,3‐ b ]indole ( ID23b‐C16 ) are reported. Both compounds exhibit wide bandgaps (>3.5 eV), high thermal stability (decomposition temperature >410 °C), and form aggregates in water:THF mixtures with distinct morphological characteristics. Using simple planar FTO/molecule/FTO devices, films prepared from pre‐aggregated solutions achieve photoresponsivities of 32.5 mA W −1 ( ID23b‐C12 ) and 74.8 mA W −1 ( ID23b‐C16 ) at 254 nm under 2 V bias, representing 6.1 × and 20.8 × enhancements compared to molecularly dispersed films. Detectivity values reach 2.8 × 10 10 Jones and 1.3 × 10 1 1 Jones, respectively. This single‐component approach achieves performance competitive with complex donor‐acceptor heterojunctions, demonstrating solution‐state molecular organization as an effective strategy for efficient deep‐UV photodetection without elaborate device engineering.