Simultaneous Enhancement of Electrochromic Performance and Infrared Modulation in PANI-TiO₂ Composites

Polyaniline (abbreviated as PANI), a promising electrochromic material, exhibits broad optical tunability and rapid switching time. However, the prolonged preservation of its leucoemeraldine state is hindered by the high thermodynamic stability of its emeraldine salt state. In this work, density functional theory calculation reveals that titanium oxide doping substantially elevates both the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels in oxidized PANI-TiO2 composites, facilitating electron excitation and polaron formation. Coupled with expanded electrochemical active surface areas and enhanced ion transport efficiency, the synthesized PANI-TiO2 composite films achieve an optical contrast of 73.8%. The coloration and bleaching time of PANI-TiO2 composites was determined to be 0.46 and 0.94 s, respectively, significantly surpassing those of pure PANI films. Moreover, the composites demonstrate exceptional infrared modulation capabilities, exhibiting an emissivity variation (Δε) of 0.61 under low-voltage stimuli (≤1 V). These findings provide a fundamental insight into the structural engineering strategies for advanced electrochromic materials.