Photoinduced charge-carrier dynamics of phototransistors based on perylene diimide/reduced graphene oxide core/shell p-n junction nanowires

Abstract

The tailored fabrication of multicomponent nanostructures that can exhibit superior or unique optoelectronic properties compared with those of the single-component system is highly desirable for fundamental studies of charge transport mechanisms and novel applications with advanced functions. To achieve efficient charge transport and high photoresponsivity, core/shell p-n heterojunction nanowires (NWs) are fabricated using N,N′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide (BPE-PTCDI) and reduced graphene oxide (rGO) in solution phase. BPE-PTCDI/rGO core/shell NWs exhibit significantly enhanced photocurrent and faster charge compensation rate under irradiation, compared with pure BPE-PTCDI NWs. BPE-PTCDI NW core mainly acts as a light absorption layer, whereas rGO shell functions as a charge transport channel and contributes to a large electrical conductivity. Accordingly, the outstanding light-detecting performance of BPE-PTCDI/rGO NWs results from the synergistic combination of the favorable optical and electrical properties of each of the constituent materials. Intriguingly, BPE-PTCDI/rGO NW organic phototransistors (OPTs) show charge compensation behaviors opposite to those of pure BPE-PTCDI NW-OPTs, which is interpreted with a model concerning charge trapping energy levels. The results obtained herein demonstrate great promise for use of carbon-based multicomponent core/shell nanomaterials in photodetectors, and the developed methodology provides insights into the quantitative analysis of the photogenerated charge-carrier dynamics of multicomponent semiconducting systems. Multicomponent phototransistors prepared using perylene diimide/reduced graphene oxide core/shell p-n heterojunction nanowires exhibit ambipolar charge transport, high photoresponsivity, and photocurrent multiplication, due to the synergistic interplay of the core and shell materials. The photoinduced charge-carrier dynamics are investigated by analyzing charge compensation rates and external quantum efficiencies, which are superior to those of the single-component system