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 m(2) 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.