High performance n-type vertical organic phototransistors

Abstract

Abstract In this manuscript, a solution-processed n-type organic phototransistor based on vertical structure thin-film transistors was proposed. Due to the vertical structure and short channel length (≈130 nm), the transistors exhibited excellent current density (15.4 mA/cm2) with high Ion/Ioff ratio (up to 105). On account of this structure, the face-on π-π stacking of P(NDI2OD-T2) was aligned with the charge transport direction, which facilitated charge transfer from source to drain electrode. Moreover, n-type organic phototransistors based on vertical thin-film transistors were demonstrated for the first time, in which the active layer was protected by the source-drain electrodes, resulting in the improvement of the stability of the device. Due to the nanoscale channel, efficient separation of electron-hole pairs and quick charge transfer can be achieved. Hence, high-performance n-type phototransistor was obtained with responsivity of 34.8 A/W, photosensitivity of 4.78 × 104, detectivity of 3.95 × 1013 Jones and external quantum efficiency up to 1.1 × 104% under 400 nm illumination with a light intensity of 200 μW cm−2, which was much better than those reported n-type organic phototransistors. This work provided a strategy for the fabrication of high performance n-type organic phototransistor, which paved the way for its future application in the next-generation organic optoelectronics.