Multi‐Shell Porous TiO2 Hollow Nanoparticles for Enhanced Light Harvesting in Dye‐sensitized Solar Cells

An optimized configuration for nanomaterials in working electrodes is vital to the high performance of dye‐sensitized solar cells (DSSCs). Here, a fabrication method is introduced for multi‐shell TiO₂ hollow nanoparticles (MS‐TiO₂‐HNPs) via a sol–gel reaction, calcination, and an etching process. The prepared uniform MS‐HNPs have a high surface area (ca. 171 m² g^?1), multireflection, and facile electrolyte circulation and diffusion. During the MS‐HNP fabrication process, the amount of SiO₂ precursor and H₂O under reaction has a significant effect on aggregation and side reactions. The etching process to obtain pure TiO₂ is influenced by anatase crystallinity. Additionally, single‐shell (SS)‐TiO₂‐HNPs and double‐shell (DS)‐TiO₂‐HNPs are synthesized as a control. The MS‐TiO₂‐HNPs exhibit a high surface area and enhance light reflectance, compared with the SS‐ and DS‐TiO₂‐HNPs of the same size. The power conversion efficiency of the optimized MS‐TiO₂‐HNP‐based DSSCs is 9.4%, compared with the 8.0% efficiency demonstrated by SS‐TiO₂‐HNP‐DSSCs (a 17.5% improvement). These results enable the utilization of multifunctional MS‐HNPs in energy material applications, such as lithium ion batteries, photocatalysts, water‐splitting, and supercapacitors.