Infrared emission characteristics of electrochromic thin films based on polyaniline

To apply polyaniline thin films in electrochromic devices and optimize their performance, sulfuric acid(H₂SO₄) and sulfosalicylic acid(SSA) co-doped electrochromic films based on polyaniline were prepared by potentiostatic method on flexible PET-ITO films. The physical properties of the films were studied by scanning electron microscopy(SEM), infrared emissivity tester, FTIR spectroscopy, four-probe meter and UV-Vis spectrophotometer. The influences of electrolyte concentration ratio and temperature on the performance of PANI films were particularly discussed. To study the infrared emission characteristics of polyanline thin films and find key factors for emissivity changing in deposition process, resistance-emissivity curves (R-E curves) were given and their relationship with emissivity variability was discussed. Based on emissivity variance, electrochromic performance in visible lights were observed. R-E curves confirmed that the relationship between infrared emissivity and resistance follows logarithmic function depending on the effective thickness of the films and the conducting structure of the polymer, which can strongly affect the emissivity variability of polyaniline thin films. With the increase of original emissivity (E₀), the variability ΔE first increased, and reached the highest value when E₀ was 0.71. After that ΔE reduced. The results of UV-Vis spectra confirmed that the films could realize good emissivity variability and at the same time get high contrast of visible lights (ΔT%) between coloring and bleaching. When E₀ is 0.71, the ΔT% at average of visible light wavelength is 43.8%.