Defect chemistry, self-modified Ti³⁺-doped TiO₂ as a photoanode material for dye-sensitized solar cell

To meet the energy demand of modern society, we vote in renewable energy source particularly dye-sensitized solar cells (DSSC). In this regard, the efficiency of DSSCs was improved by self-doped Ti³⁺ on Titanium dioxide (TiO₂) surface. The integration of Ti³⁺ resulted in formation of oxygen vacancy that leads to generation of free electron. The formation of oxygen vacancy and free electron are observed in X-ray photo spectroscopy and the Electron Spin Resonance spectra. Further, oxygen vacancies in TiO₂ have helped in retards the photo-generated electron and hole pairs and fine-tuned the agglomerated particles into uniform particles. The presence of oxygen vacancies increases the local charge density of free electron, and this energy level of oxygen vacancy can serve as electron donor states. Markedly, the maximum photo-conversion efficiency of 6.5% was achieved for Ti³⁺-incorporated TiO₂ photoanode with the open-circuit voltage (V_oc) of 0.759 Voltage (V) and short-circuit current (J_sc) of 10.5 mA/cm², whereas the pristine photoanode showed maximum photo-conversion efficiency of 5.0% with V_oc of 0.767 V and J_sc of 8.6 mA/cm². The increase in photo-generated electron–hole pair was also validated by transient photocurrent measurement and impedance spectra. The results indicate the importance of the vacancies present in the metal oxide for developing DSSCs with high efficiency.