Photoexcitation of neodymium doped TiO2 for improved performance in dye-sensitized solar cells

• Physical process of pulverization has been attempted to cause surface level doping.
• Lanthanide doping facilitates the formation of impurity levels and band gap narrowing leading to visible light absorption
• Photoexcitation of the doped semiconductor and the dye leads to reduction in recombination.
• Higher negative flat-band potential and favorable alignment of energy levels further enhances Jsc and Voc.

A series of Nd-doped TiO2 with Nd content ranging from 1 to 5 at.% were synthesized by solid state technique and explored as a photoanode material in dye-sensitized solar cells (DSSCs). Incorporation of Nd3 + into TiO2 lattice resulted in more negative flat band potential for Nd-doped TiO2 than pure TiO2, as determined by impedance spectroscopy (Mott–Schottky plots), which is highly desirable to achieve higher Voc in DSSCs. In addition, Nd doping in TiO2 provided the opportunities to engender higher density of oxygen vacancies and bang gap narrowing in Nd-TiO2 photoanode, which collectively enhanced the optical properties of photoanode DSSC in terms of higher dye loading and light absorption respectively. A best efficiency of 6.17% was achieved with 4% Nd-doped titania, resulting in a remarkable increase in efficiency (102.3%) of the device over the undoped titania cells. Induction of intermediate bands, realignment of energy levels leading to a better electron injection, high sensitizer loading, efficient charge separation due to dopant and its impurity levels contribute favorably towards the superior performance of Nd doped TiO2 DSSC. Spectroscopy (EIS) measurements showed Nd doped TiO2 photoanode possessed higher charge recombination resistance and longer electron lifetime compared to DSSCs with undoped TiO2.

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