Electrical and photoelectrical properties of polymer single nanowire made of diketopyrrolopyrrole-based conjugated copolymer bearing dithieno[3,2-b: 2′,3′-d]thiophene

We demonstrated a diketopyrrolopyrrole (DPP)-based alternating copolymer (i.e., PDTTDPP) which contains planar dithieno[3,2-b:2′,3′-d] thiophene (DTT) unit and high effectiveness in the fabrication of solution-based polymer nanowires (PNWs). PDTTDPP was found highly crystalline and exhibited optimized energy levels for p-type semiconductor. The electrical properties of single PNWs such as specific resistivity (ρ) and photoresponsivity (R) were investigated by measuring the dark current and photocurrent under visible and near-infrared lights. These electrical properties were compared for high (HA-PNW) and low (LA-PNW) aspect ratio PNWs produced using two different preparation methods such as membrane wetting method and self-assembly in a dilute solution. The measured responsivity (R) values of single HA-PNW at +40 V are 134 and 114 A W^-1 at 632 and 830 nm, respectively. In contrast, the R values of LA-PNW under identical conditions were determined to range from 0.55 A W^-1 to 0.65 A W^-1 (λ = 632 nm) and from 0.61 A W^-1 to 0.73 A W^-1 (λ = 830 nm) at a +40 V bias voltage, which are significantly lower than those of HA-PNW-based devices.