Herein, we report the impact of chromium doping on the physical properties, electronic band structure and photovoltaic characteristics of their corresponding devices based on dye-sensitized solar cells (DSCs). Different DSCs with various compositions of the photoanode electrodes are fabricated to study their optical, structural, conduction band edge, donor density, depth of trap states and photoelectrochemical properties using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), Mott-Schottky capacitance analysis, chemical capacitance and electrochemical impedance spectroscopy (EIS) measurements. For such studies, the Cr-doped TiO2 films, with different Cr : Ti atomic ratios of 0.1-5% and a particle size in the range 15-30 nm, are synthesized by a facile hydrothermal process. We find that on introduction of Cr3+ into the TiO2 lattice, the films exhibit small band gap, an upward shift in the conduction and valence band edges, and a low donor density. The results show that the Cr-doped TiO2 electrodes have a lower recombination rate, a superior electron lifetime and a higher open circuit voltage than pristine TiO2. However, these electrodes show a poor dye adsorption due to the surface defects of Ti3+ and the charge transport characteristics, resulting in a low short-circuit current. Furthermore, doping of TiO2 with chromium may induce a high density of empty trap states with a deep position, leading to an entrapment of the charge carriers, a drop in electron conductivity and, therefore, an inferior photovoltaic performance of the solar cells.
ASJC Scopus subject areas
- Materials Chemistry