Improved photomultiplication in inverted-structure organic photodetectors via interfacial engineering

Organic photodetectors with photomultiplication, i.e., ultrahigh gain, have drawn extensive attention. Here, we report poly(3-hexylthiophene):3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene)-based organic photodetectors with a structure of indium tin oxide/interlayer/active layer/MoOx/Al. With the selection of appropriate bottom electrode interlayer materials such as ZnO, PFN, and K2CO3, the devices show ultrahigh gain over the entire measured spectral range and good long-term stability. An optimized device with a ZnO interlayer exhibits a superior external quantum efficiency (EQE) of 19 300% at 360 nm, a detectivity of 2.15 × 1012 Jones at 600 nm, and a linear dynamic range of 98.36 dB under a bias voltage of −20 V. Moreover, the device also shows improved long-term stability that preserves 70% of its initial EQE after 120 h in the ambient environment without encapsulation.