Enhanced photocurrent of nitrogen-doped TiO2 film for dye-sensitized solar cells

Nitrogen (n)-doped titanium dioxide (TiO2) was prepared with varying doping extent by a general sol–gel process with a pure TiO2 film as the control sample. The n-doped-2 electrode showed the maximum conversion efficiency with an open-circuit voltage (Voc) of 0.726 V, a photocurrent (Jsc) of 10.52 mA cm−2, a fill factor of 63.6%, and an efficiency of 4.86%, compared to 0.751 V, 7.4 mA cm−2, 67.1%, and 3.73%, respectively, for the undoped (u-doped) TiO2 electrode. The approximate 23% enhancement in the conversion efficiency of the n-doped-2 TiO2 electrode-based dye-sensitized solar cells (DSSCs) was mostly ascribed to the increase of light absorption in the near-vis absorbance and partially to the morphological characteristics of the n-doped TiO2 film. Additionally, the doping type of nitrogen in the TiO2 lattice was closely studied using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The relation between the doping type and the electron behavior in the DSSCs was also examined.