Photolithographic PEDOT:PSS Electrodes for Transparent and Conformal Organic Transistors

Poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) is widely used as electrode material for transparent and conformal organic thin-film transistors (TC-OTFTs) owing to its excellent conductivity, high transparency, and good mechanical flexibility. However, due to the lack of high-precision and high-density transparent flexible electrodes, the high-level integration of TC-OTFTs faces a huge challenge. Here, we propose a simple protective layer photolithography strategy that successfully achieves non-destructive photolithography of PEDOT:PSS. The pattern feature size is down to 750 nm, which is the smallest size of PEDOT:PSS reported so far. Based on such high-precision transparent electrodes, we successfully fabricate TC-OTFTs with a device density up to 50,020 transistors <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{cm}}^{-{2}}$ </tex-math></inline-formula>, which is the highest value reported for TC-OTFTs. More strikingly, the device showcases outstanding mobility of 1.51 cm2<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\text{V}}^{-{1}} {\text{s}}^{-{1}}$ </tex-math></inline-formula>. This work provides a reliable photolithography strategy to realize scalable fabrication and high-density integration of TC-OTFTs, offering a significant potential for developing wearable invisible electronics with high density and performance.