Performance enhancement of an organic photodetector enabled by NPB modified hole transport layer

Abstract

Transport layers are extremely important for organic photodetectors (OPDs) due to their effective role in improving the charge selectivity at the contacts, thus leading to high photoresponse and low dark current. The quintessential hole transport layer (HTL), e.g. MoO3, is suffering from the work function instability caused by the preparation process and the evolution in external environment. In this paper, we introduce an N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) interfacial layer to modify MoO3 HTL. At an optimized NPB thickness of 20 nm, the photocurrent (J p) density of the device increases by 19%, thus the responsivity and external quantum efficiency are raised to 0.44 A W−1 and 75% at 725 nm. Besides, owing to the suppressed dark current, the optimized device showcases an enhanced specific detectivity of over 1011 Jones in the range of 460–750 nm (under negative bias). This achievement is assigned to the improvement in transport and collection efficiency of holes. The study provides a feasible method of HTL modification to improve the performance of OPDs.