A simple spray reaction synthesis and characterization of hierarchically porous SnO2 microspheres for an enhanced dye sensitized solar cell

Abstract

This paper reports first on the novel synthesis of hierarchical tin dioxide (SnO₂) porous microspheres in the absence of a template using a simple spray reaction technique and annealing at 500–800 °C. The SnO₂ microspheres obtained are tetragonal phase and approximately 2.2–2.7 μm in diameter, and they consist of 6.7–23.1 nm crystallites and possess hierarchical pores and Brunauer–Emmett–Teller (BET) surface areas of up to 55 m² g⁻¹. Using ultraviolet-visible absorption spectra analysis, it is found that SnO₂ crystallites demonstrate a quantum size effect, resulting in a widening of the band gap of the SnO₂ spheres. This band gap can be tuned from 3.99 eV (800 °C) to 4.26 eV (600 °C) by varying the annealing temperature. Using separated SnO₂ porous spheres as the scattering layer of the photoanode for dye sensitized solar cells (DSSCs), the solar light-electricity conversion efficiency (maximum: 6.0%) is increased by up to 31.9% and 28.2% compared to cells using a commercial SnO₂ powder and P25 nanopowder as the scattering layers, respectively, under the same conditions.