High‐Performance Flexible Electronics Fabricated Using a Surface Energy‐Directed Assembly Process on Ultrathin Polyimide Substrates

Abstract Solution‐based processes are emerging in the fabrication of flexible electronics owing to their cost‐effectiveness, low‐temperature processing capabilities, and vacuum‐free operations. Currently, printing techniques, as the most widely used solution‐based processes, suffer from low resolution and poor pattern fidelity. Although surface energy‐directed assembly (SEDA) process enables unparalleled resolution and fidelity, multilayer fabrication and application on flexible substrates are rarely attempted. Here, a SEDA process is used for fabricating metal oxide thin film transistors (TFTs) on ultrathin and flexible polyimide (PI) substrates with a thickness of ≈35 µm. Comprehensive procedures to render PI substrates hydrophobic as well as to homogenize the hydrophobicity of the PI substrates and as‐assembled layers are developed. All‐solution‐processed flexible TFTs are constructed by assembling indium oxide semiconducting channels, indium tin oxide source/drain electrodes, aluminum oxide gate dielectric layers, and indium tin oxide gate electrodes ordinally. The metal oxide TFTs exhibit excellent electrical properties with an average mobility of 22.01 cm² V⁻¹ s⁻¹ and stable operation under mechanical strain. Flexible inverters with a high voltage gain of 78 and a high dynamic operation frequency of up to 1 kHz are also constructed, representing new opportunities of the SEDA process for the fabrication of next‐generation flexible electronics.