Enhancing the performance of poly(3-methylthiophene)-based electrochromic devices via insertion of a TiO2 buffer layer

Anatase-titanium dioxide (TiO2) nanoparticles were spin-coated on indium-tin oxide (ITO) glass substrates to fabricate TiO2 films through annealing at 450 °C/30 min. 3-Methylthiophene (3MT) was electrochemically deposited onto mesoporous TiO2 films to form poly(3-methylthiophene) (P3MT/TiO2) composite electrochromic electrodes. The introduction of TiO2 mesoporous films enhanced the adhesion of P3MT polymers to the TiO2/ITO substrate, thereby increasing the long-term stability of the corresponding electrochromic devices. Experimental results reveal that P3MT/TiO2 composite electrodes retained up to 84% of the maximum optical contrast (ΔT%), relative to 56% remaining ΔT% of pure ITO electrodes. This illustrates the enhanced long-term stability achieved through the introduction of a TiO2 buffer layer in electrochromic devices. These devices demonstrated excellent response time characteristics and ΔT% value of 4 s and ca. of 70%, respectively. This work has shown that conductive polymer/TiO2 composite electrodes are well suited to electrochromic devices for the promotion of performance and stability.