Deposition of inverse opal-like TiO₂ thin film with enhanced photoelectrochemical activity by a spin-coating combined with a dip-coating method

TiO₂ thin films with an inverse opal-like structure have attracted considerable attention recently owing to their high potential for a range of applications. In this study, we demonstrated the possibility to deposit TiO₂ thin films with an inverse opal-like structure from TiO₂ nanoparticle-based slurry paste using a conventional spin-coating process. In addition, we also showed that the photoelectrochemical (PEC) performance of as-fabricated inverse opal-like TiO₂ films can be further improved by the dip-coating process. In particular, dip-coated and untreated inverse opal-like TiO₂ films exhibit photocurrent densities of ∼66.5 μA cm⁻² and ∼40.9 μA cm⁻² at 1.23 V versus RHE, respectively. A detailed physicochemical analysis revealed that photocurrent density enhancement (∼38.5%) in dip-coated inverse opal-like films can be attributed to a variety of factors including improved interconnection between TiO₂ nanoparticles, higher crystallinity, decreased light reflection, and reduced charge carriers recombination. We strongly believe that these findings will be useful in the development of highly efficient third-generation solar cells, photocatalytic systems, electrochromic devices, and gas sensors.