Zn2SnO4-Based Dye-Sensitized Solar Cells: Insight into Dye-Selectivity and Photoelectric Behaviors

Abstract

Infrared dyes in dye-sensitized solar cells (DSCs) usually mismatch with the band structure of TiO2. This mismatch subsequently results in insufficient kinetics in charge separation. Researchers have started focusing on ternary oxide semiconductors because of their stability. Moreover, the chemical compositions and band structures of these semiconductors are easy to control. In this paper, a ternary semiconductor oxide, Zn2SnO4, was synthesized through a hydrothermal method and used as a photoanode for DSCs. Zn2SnO4 selectivity toward organic and ruthenium complex dyes was different from that of TiO2. Zn2SnO4–DSCs performance was improved at a greater degree with organic sensitizer 2-cyano-3-{4-[2-(4- diphenylamino-phenyl)-vinyl]-phenyl}-acrylic acid (TPC) than with cis-bis (isothiocyanato)-bis (2,2-bipyridyl- 4,4-dicarboxylato) ruthenium (II) bis-tetrabutyl-ammonium (N719). We further improved the power conversion efficiency of Zn2SnO4-DSCs to 5.72% through surface modification and structural optimization. Stepped light-induced measurement of photocurrent and photovoltage was used to systematically study electron behaviors in surface-modified and unmodified Zn2SnO4-based and TiO2-based DSCs. Zn2SnO4 exhibited higher electron diffusion coefficient than TiO2. The electron lifetime of Zn2SnO4-based DSCs increased after surface modification.