A Critical Review on Photomultiplication Type Organic Photodetectors

This review systematically summarizes the development, working mechanism, performance optimization and relevant application exploration of photomultiplication type organic photodetectors (PM-OPDs). In 2015, Prof. Fujun Zhang's group firstly reported PM-OPDs on the basis of active layers with single carrier transport channels. Electron traps are formed with acceptor surrounded by donor in active layers with the weight ratio of donor to acceptor as about 100:1. The working mechanism of PM-OPDs is attributed to hole tunneling injection assisted by interfacial trapped electron. Dark current density of PM-OPDs can be well suppressed due to the single carrier transport in active layers with rather less acceptor. New concept of "charge injection narrowing" was firstly proposed to prepare ultra-narrowband PM-OPDs, which is realized by adjusting thickness of active layers to control interfacial trapped electron distribution. Broadband PM-OPDs can be obtained via ternary strategy or double-layer scheme. Double-layer scheme consists of one absorption layer and one PM layer, which are individually employed to tune spectral response range of PM-OPDs and achieve external quantum efficiency greater than 100%. The advantages of photodiode type photodetectors and PM-OPDs can be integrated into one device by employing double-layer scheme. PM-OPDs with broad and flat spectral response can be achieved via optimizing interfacial trapped electron distribution, which can be regulated by inserting optical field adjusting layer or incorporating wide bandgap semiconductor materials into active layers. The PM-OPDs have been successfully applied in many fields, such as heart rate monitoring, single pixel imaging and optical switch. The successful practical applications indicate good development prospect of PM-OPDs. [GRAPHICS] .