Enhancement of Charge Transport of a Dye-Sensitized Solar Cell Utilizing TiO2 Quantum Dot Photoelectrode Film

A dye-sensitized solar cell (DSC) is the third generation of solar technology, utilizing TiO2 nanoparticles with sizes of 20-30 nm as the photoelectrode material. The integration of smaller nanoparticles has the advantage of providing a larger surface area, yet the presence of grain boundaries is inevitable, resulting in a higher probability of electron trapping. This study reports on the improvement of charge transport through the integration of quantum dot (QD) TiO2 with a size of less than 10 nm as the dye absorption photoelectrode layer. The QD TiO2 samples were synthesized through sol-gel and reflux methods in a controlled pH solution without surfactants. The synthesized samples were analyzed using microscopic, diffraction, absorption, as well as spectroscopic analyses. A current-voltage and impedance analysis was used to evaluate the performance of a DSC integrated with synthesized TiO2 as the photoelectrode material. The sample with smaller crystallite structures led to a large surface area and exhibited a higher dye absorption capability. Interestingly, a DSC integrated with QD TiO2 showed a higher steady-state electron density and a lower electron recombination rate. The shallow distribution of the trap state led to an improvement of the electron trapping/de-trapping process between the Fermi level and the conduction band of oxide photoelectrode material, hence improving the lifetime of generated electrons and the overall performance of the DSC.