Synergistic azo–phthalocyanine heterojunctions for broadband photomultiplication organic photodetectors

Near-infrared organic photodetectors have shown significant application potential in the fields of flexible optoelectronics and weak-light sensing. Among them, azo-based photoelectric materials occupy an important position in optoelectronic applications owing to their facile preparation and low dark current characteristics. However, azo-based photoelectric materials generally suffer from insufficient absorption in the long-wavelength region and severe carrier recombination. To address these issues, a bulk heterojunction was constructed in this work by incorporating VONc into a triphenylamine-based azo photosensitive molecule (Tazo-1), thereby developing a photomultiplication-type broadband organic photodetector. Tazo-1@VONc composite films were prepared via a solution-processing method, and devices with an Au/ p -TPD/active layer/ITO architecture were fabricated to systematically investigate their optical, electrochemical, and photoelectric properties. Research shows that the photodetector based on Tazo-1@30%VONc (Tazo-1@30%VONc-PD) exhibits excellent photodetection properties from 365 nm to 940 nm. At a low intensity of 0.01 mW cm −2 , the EQE at 400 nm is as high as 1278%, and the R at 600 nm is 4836 mA W −1 . Compared to Tazo-1-PD, Tazo-1@30%VONc-PD exhibits remarkably enhanced performance in the near-infrared region, with the EQE and R increased by 22.7-fold (700 nm), 40.7-fold (765 nm), 49.8-fold (850 nm), and 459-fold (940 nm). This study reveals the critical role of the azo–phthalocyanine synergistic system in interfacial trap regulation and the photomultiplication mechanism, providing a new strategy for the molecular design and device optimization of high-performance broadband organic near-infrared photodetectors.