La2O3-encapsulated SnO2 nanocrystallite-based photoanodes for enhanced DSSCs performance

Abstract

A SnO₂ nanocrystallite-based photoanode was prepared using tin (IV) chloride and fructose via a one-pot hydrothermal method, and its structural and morphological properties were studied. Structural observations revealed tetragonal crystals of SnO₂, and morphological studies confirmed the presence of spherical nanoparticulates. Furthermore, encapsulating the surface of the SnO₂ photoanode (+N719 dye) with thin layers of La₂O₃ significantly improved the short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency values from 8.30 to 13.70 mA cm⁻², 0.40 to 0.46 V, 49% to 48% and 1.66% to 3.0%, respectively. The nearly two-fold improvement in energy conversion efficiency was attributed to: (a) increased dye molecules caused by the formation of strong co-ordination bonds between the dye molecules and the lanthanide, (b) enhanced photoelectron transfer rate between the dye molecules and SnO₂ conduction band, and (c) negative shift of SnO₂ conduction band position in the presence of La₂O₃ (confirmed from the Mott–Schottky and Tafel measurements).