Visible-Blind Ultraviolet Narrowband Photomultiplication-Type Organic Photodetector with an Ultrahigh External Quantum Efficiency over 1000000%
Dechao Guo, Liqing Yang, Jingcheng Zhao, Ji Li, Guo He, Dezhi Yang*, Linge Wang,* Agafonov Vadim,and Dongge Ma*
Mater. Horiz., 2021, 8, 2293-2302.
The visible-blind ultraviolet (UV) photodetector can detect UV signals and is not interfered by visible light or infrared light in the environment. In order to realize high-performance visible-blind UV organic photodetectors (OPDs), we design photomultiplication-type (PM-type) OPDs by using novel strategy. Firstly, wide bandgap organic semiconductor materials, which do not absorb visible light, are selected as donors to absorb UV light. Secondly, a very small amount of C60 is used as acceptor to trap photogenerated electrons. These accumulating electrons near the Al electrode form a potential, which leads to band bending and narrowing of the interface barrier, thereby assisting hole-tunneling injection to form a multiplication. The fabricated visible-blind UV PM-type OPDs with donor/acceptor doping ratio of 50:1 exhibit a narrowband response with full-width at half-maximum (FWHM) of approximate 36 nm, an ultrahigh external quantum efficiency of 1.08×106% and a remarkable specific detectivity of 1.28×1014 Jones at 335 nm wavelength under -14 V bias. The UV-to-visible rejection ratio exceeds 103 by adjusting the donor/acceptor mixing ratios. The devices made with other wide bandgap organic materials also showed similar performance, indicating that this device structure provide an effective method for the preparation of high-performance visible-blind UV PM-type OPDs. In addition, we prepared a flexible visible-blind UV PM-type OPD based on PET substrate and integrated it with a flexible OLED to fabricate a wearable UV monitor, which can visually detect the intensity of UV light.