Photovoltaic performance of Ti-doped BiOCl semiconductor photoanodes sensitized with N3 and N719 dyes for dye-sensitized solar cells

Abstract

Bismuth oxychloride (BiOCl) is a layered semiconductor with potential for use as a photoanode material in dye-sensitized solar cells (DSSCs); however, its photovoltaic response is limited by its wide band gap and restricted visible-light absorption. In this study, pure BiOCl and Ti-doped BiOCl photoanodes with nominal Ti/Bi atomic ratios corresponding to 1.59 at.%, 2.34 at.%, and 4.19 at.% were synthesized by a chemical co-precipitation method and investigated in DSSCs sensitized with N3 and N719 dyes. X-ray diffraction and Raman analyses confirmed the formation of tetragonal BiOCl without detectable secondary phases. UV–visible analysis showed a gradual decrease in the optical band gap from 3.28 eV for pure BiOCl to 3.12 eV for 4.19 at.% Ti–BiOCl. FESEM analysis revealed hierarchical microsphere-like structures composed of interconnected nanosheets, which may provide favorable surfaces for dye adsorption and electrolyte diffusion. Photovoltaic measurements under AM 1.5G illumination showed that Ti incorporation modified the photovoltaic response of BiOCl photoanodes. The 4.19 at.% Ti–BiOCl photoanode produced PCEs of 0.452% and 0.424% for N3- and N719-sensitized DSSCs, respectively, compared with 0.384% and 0.393% for pure BiOCl. Although Ti incorporation improved the PCE relative to pure BiOCl, the absolute efficiencies remained limited. These results indicate that Ti incorporation can modify the structural, optical, and photovoltaic properties of BiOCl, while further optimization of dye loading, photoanode thickness, interfacial charge transfer, electrolyte composition, and device architecture is required to improve the overall DSSC efficiency.