Fabrication And Feild-Effect Properties Of Organic Semiconductor Nanowires Using Nanotransfer Moulding Technique

One-dimensional nanowires are emerging as promising materials to produce high-performance nanoscale phototransistors. In a one-dimensional ordered nanostructure, photo-induced charge transfer can improve both the separation and transportation of charge carriers, which are the key factors that determine optoelectronic device performance.Single-component near-infrared phototransistors based on ambipolar organic semiconductor nanowires have been investigated and compared with their corresponding thin-film counterparts. The ambipolar NIR phototransistor exhibited both hole-carrier and electron-carrier transport and an obvious photoresponse to different intensities of the NIR illumination. The nanowire organic phototransistors (NW-OPTs) showed photocurrent/dark-current ratios and photoresponsivities as high as 1.3×104 and 440 mA/W for the p-type channel, and 3.3 × 104 and 70 mA/W for the n-type channel, respectively, upon near-infrared illumination with an intensity of 47.1 mW/cm2. These were much higher values compared to their thin-film counterparts. The normalized mobility enhancement of NW-OPTs in the dark increased up to four times upon NIR illumination at the intensity of 47.1 mW/cm2. This number is dozens of times higher than the one for thin-film OPTs. The enhancement of near-infrared photoresponse could be attributed to the larger trap density originated from the semiconductor/insulator interface and semiconductor/air interface. These results were mainly caused by doping effects in which the large surface-to-volume ratio of the nanostructures generates more trap sites, and photo-induced charge-injection behaviors arising from the bottom-contact configuration as well. The performance of NW-OPTs was demonstrated to open new possibilities to improve near-infrared photoresponse of single-component devices.