Ultrafast Speed, Dark Current Suppression, and Self-Powered Enhancement in TiO2-Based Ultraviolet Photodetectors by Organic Layers and Ag Nanowires Regulation.

Abstract

TiO2-based photodetectors (PDs) have been hotspots in recent years for their excellent thermal stabilities and optoelectronic performance under ultraviolet (UV) light. However, the high dark current caused by defects in TiO2 films has limited the detectivity (D) of these PDs. Here, the dark current of a TiO2-based PD was effectively reduced by 3 magnitudes (from 0.1 mA to 20 nA) and D was increased to 1.2 × 1014 Jones by introducing PC71BM. The TiO2/PC71BM heterojunction also made the PD self-powered, and by further introducing an interface layer of PEDOT:PSS and finely optimizing the electrode Ag nanowires (Ag NWs), the self-powered responsivity (R) was increased to 33 mA/W. Ultrafast rise/decay times (129 ns/1 ms at -1 V and 0.06 s/<1 μs at 0 V) were achieved. This work successfully applied an organic-inorganic heterojunction, an organic interface, and Ag NWs to suppress the dark current and enhance the self-powered photocurrent/R of inorganic PDs, providing a feasible strategy in high-performance UV PDs' design.