Microstructure Regulation and Optoelectronic Performance Optimization of Flexible CPI-Based ITO Thin Films under Low-Temperature Heat Treatment Process

Addressing the urgent need for low-temperature processes in the manufacturing of flexible vehicle-mounted touch display devices, this study investigates the process-structure-performance relationships of indium tin oxide (ITO) thin films prepared by DC magnetron sputtering at temperatures far below the tolerance limit of transparent polyimide (CPI). By systematically adjusting the substrate temperature (30-300°C) combined with 230°C atmospheric annealing, a unique optimization effect was identified at the moderate deposition temperature of 110°C. Experimental results show that the sample deposited at 110°C followed by annealing exhibits optimal comprehensive performance: resistivity as low as 203 μΩ·cm, average visible light transmittance of 89.2%, surface roughness of 0.76 nm, and the ability to endure 100,000 bending cycles at a bending radius of R = 5 mm with a sheet resistance change rate of less than 10%. Microstructural analysis reveals that this process facilitates the complete conversion of Sn²⁺ to Sn⁴⁺ and the controlled formation of oxygen vacancies, leading to a synergistic improvement in carrier concentration (8.7×10²⁰ cm⁻³) and mobility (35.2 cm²/V·s). This work elucidates the crystallization kinetics and doping mechanisms of ITO thin films under low-temperature conditions, offering important theoretical foundations and technical pathways for the low-temperature fabrication of high-performance transparent electrodes in flexible vehicle-mounted touch display devices.