Physicochemical properties of Cr-doped TiO2 nanotubes and their application in dye-sensitized solar cells

Doping is always known as an effective way to modify the properties of a semiconductor. In this work, Cr-doped TiO2 nanotubes (Cr-TNTs) with different Cr contents were synthesized via a microwave-assisted hydrothermal method. The changes in crystal structures, chemical and electronic states, and the band gap structure of the obtained Cr-doped TiO2 nanomaterials were analyzed, thereby confirming the effect of the doping on physicochemical properties of the products. Moreover, the existence of Ti3+ sites and oxygen vacancies have significantly influenced the separation of electron-hole pairs as predicted by the photoluminescence spectra. The EIS results indicated that Cr-doping on TNT made a significant contribution to reducing the recombination rate of photogenerated charge carriers, leading to a prolonged lifetime of photogenerated electrons. The Cr-TNT based dye-sensitized solar cell (DSSC) containing 7.5 atomic percentage of Cr/Ti has demonstrated the best efficiency on the solar light conversion among the prepared samples.