One-pot synthesis of hierarchical mesoporous SnO2 spheres using a graft copolymer: enhanced photovoltaic and photocatalytic performance

Abstract

We synthesized hierarchical mesoporous SnO₂ (HM-SnO₂) spheres with a large surface area (85.3 m² g⁻¹) via a one-pot controlled solvothermal process using tin chloride pentahydrate and graft copolymer, i.e., poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) as a Sn precursor and structure directing agent, respectively. Solid-state dye-sensitized solar cells (ssDSSCs) fabricated with HM-SnO₂ spheres on an organized mesoporous SnO₂ interfacial (om-SnO₂ IF) layer as the photoanode had a long-term stable efficiency of 3.4% at 100 mW cm², which was much higher than that of ssDSSCs with a photoanode comprising nonporous SnO₂ (NP-SnO₂) spheres (1.9%). We attributed the enhanced device performance of ssDSSCs fabricated with the HM-SnO₂ photoanode to the well-organized hierarchical structure with dual pores (23.5 and 162.3 nm), which provided a larger surface area, improved light scattering, and decreased charge recombination compared to the nonporous SnO₂ (NP-SnO₂) photoanode. We confirmed this by reflectance, incident photon to current conversion efficiency (IPCE), and intensity modulated photocurrent/voltage spectroscopy (IMPS/IMVS) measurements. Introduction of an om-SnO₂ IF layer between the HM-SnO₂ spheres and fluorine-doped tin oxide (FTO) substrate enhanced light harvesting, increased electron transport, reduced charge recombination, and decreased interfacial/internal resistance. Photocatalytic tests indicated that HM-SnO₂ spheres showed high activity with good recyclability for photodegradation of methyl orange under UV light irradiation.