Lithium Incorporation into TiO₂ Photoanode for Performance Enhancement of Dye-Sensitized Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) are one of the most favorable solar cell technologies owing to their low cost and ease of fabrication. The electron transport layer, consisting of a mesoporous titanium oxide (TiO2) photoanode, plays a crucial role in DSSCs. In this study, we performed a post-lithium (Li) treatment on TiO2 films to enhance the optoelectronic features and power conversion efficiency (PCE) of DSSCs. The material properties of pristine and Li-treated TiO2 films were examined by X-ray diffraction (XRD), atomic force microscopy (AFM), steady-state photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). Li treatment was confirmed to suppress defects and enhance the crystallinity of the TiO2 films. Furthermore, TiO2 films sensitized with N719 dye were used as photoanodes and Pt as a counter electrode for the fabrication of DSSCs. The devices with 0.1 M Li-TFSI treatment showed a performance improvement of ∼20%, with a PCE of 10.5%, while the control DSSC had a PCE of 8.7%. The device performance was significantly enhanced owing to improved structural properties, efficient charge transport, and suppression of recombination owing to the passivation of trap states.