Photoinduced rapid-deposition of wafer-scale high-density semiconducting single walled carbon nanotube networks for thin-film transistors

Semiconducting single walled carbon nanotubes (s-SWNTs) have shown great promise in a variety of thin-film transistor (TFT) applications. Although several solution processing techniques have resulted in high-quality s-SWNT network films, exquisite control of film morphology at wafer-scale to achieve desired s-SWNT density and uniformity remains challenging. In addition to this hurdle is the slow s-SWNT absorbing dynamics in large-scale fabrication schemes that requires several hours to days to complete. Here, we report a photoinduced rapid-deposition technique to prepare wafer-scale s-SWNT films. Leveraging the tendency for azo-benzene materials to preferentially migrate to substrate surface under light, we utilize a light-sensitive polymer poly[(9,9-dioctylfluorenyl-2,7-diyl))-alt-co-(4,4'-azobenzene)] (PFNAB) to wrap s-‍SWNTs and accelerate s-SWNT deposition. S-SWNT networks prepared from this method affords films with high-density (>‍ 50‍ s-SWNTs per micrometer) and high-uniformity across a 4-inch wafer. More importantly, the deposition can be completed within 30 ‍minutes. Field-effect transistors comprising these s-SWNT films as active layers exhibit an on-state current of 2.44 μA μm^-1 at source-drain voltage of -1 V (V_ds=‍‍ -‍‍‍1 V), which is among the highest in reported field-effect transistors (FETs) with s-SWNT network films for TFT applications. This new photo-deposition technique is amenable for new application possibilities in s-SWNT TFT electronics.