Enhanced performance of poly(3-hexylthiophene)-based electrochromic devices by adding a mesoporous TiO2 layer

Abstract

Poly(3-hexylthiophene) (P3HT) has been proved to be an electrochromic material. It is usually deposited as a thin film on a transparent conducting (TCO) electrode to form a single or dual electrochromic devices, depending on the counter electrode structure. In this work, a mesoporous titanium oxide film (m-TiO2) is added between P3HT and TCO. Cross-sectional scanning electron microscope (SEM) images of the m-TiO2/P3HT double layer indicate that P3HT diffuses into the porous structure of m-TiO2 to become a hybrid nanocomposite layer of m-TiO2:P3HT. Cyclic voltammetry measurements of m-TiO2:P3HT show the predominant electrochromic behavior of the P3HT in the nanocomposite. Optical transmittance spectra of polarized m-TiO2:P3HT electrodes, in comparison with the single P3HT ones, show a maximum contrast increase from 25.6 % to 32.4 % for single devices and from 40.9 % to 47.1 % for dual devices. Furthermore, the kinetic optical transmittance curves of m-TiO2:P3HT-based devices give a faster switching time between bleaching and darkening, as well as a better stability for longer cycles than P3HT-based devices. It is demonstrated that the electrochromic performance is enhanced by the addition of a mesoporous TiO2 layer in electroactive polymer based electrodes.