High-Photosensitivity WSe2 Phototransistor with Electrically Self-Isolated C8-BTBT as a Light Absorption Layer

Recently, two-dimensional (2D) transition metal dichalcogenides, such as tungsten diselenide (WSe2), have been intensively explored for numerous optoelectronic applications owing to their outstanding electrical and optical properties. Although previous reports have attempted to implement high-performance phototransistors based on WSe2 through various organic molecule coatings, this method remains a key challenge since the surface charge transfer after the organic molecule coating may increase both ON and OFF currents of the device, severely limiting the signal-to-noise ratio (SNR). Here, we report a highly photosensitive WSe2 phototransistor with electrically self-isolated C8-BTBT as the light absorption layer. The self-isolated C8-BTBT on the WSe2 channel could act solely as a light absorption layer, without any electrical contribution into WSe2, resulting in a significant improvement in photosensitivity (i.e., SNR). The self-isolated C8-BTBT coating was found to improve the photosensitivity of the device by 1294% under UV light illumination (λex = 406 nm) with an incident light power density (Pinc) of 6.66 mW cm–2. Our study confirmed that this electrical self-isolation technique for the light absorption layer can be effectively used for high-performance 2D photosensing applications.