Dual-Band, Efficient Self-Powered Organic Photodetectors with Isotype Subphthalocyanine-Based Heterojunctions toward Secure Optical Communications.

High-performance heterojunction organic photodetectors (OPDs) are of great significance in optical detecting technology due to their tailorable optoelectronic properties. Herein, we designed and synthesized three n-type subphthalocyanine (SubPc) derivatives PhO-BSubPcF 12 , CHO-PhO-BSubPcF 12 , and NO 2 -PhO-BSubPcF 12 via axial nonhalogen substitution on fluorinated SubPc. These SubPc derivatives exhibit improved intramolecular charge transfer, high electron mobilities, optimized energy levels, and good thermal stability. The novel isotype p-n SubPc heterojunctions are evaluated as photosensitive layers in OPDs, which show a UV-visible dual-band response and self-powered effect. The optimal OPD with Br-BSubPc/NO 2 -PhO-BSubPcF 12 presents stable and superior performances with a high responsivity ( R ) of 0.14 A W -1 , a peak external quantum efficiency (EQE) of 30.6%, and an extremely low dark current of 0.92 nA cm -2 under a 570-595 nm illumination without a bias voltage. It has outperformed most of the reported SubPc-based OPDs. The better interfacial contact of p-n SubPc derivatives leads to a large depletion region with decreased trap densities as well as a low carrier recombination rate, which is conducive to the photoinduced carriers' separation and well-balanced transport, resulting in high device performances. Moreover, a secure communication strategy is successfully demonstrated by dual-band optimal OPD. This work is expected to provide some guidance for molecular engineering and device performance toward multifunctional electronics.