Anatase TiO2nanocrystals enclosed by well-defined crystal facets and their application in dye-sensitized solar cell

Abstract

Anatase TiO₂ nanocrystals enclosed by well-defined {101} and {001} crystal facets were prepared via a facile hydrothermal method using H⁺ exchanged potassium titanate nanowires (H-KTNWs) as precursors. The size and shape of the nanocrystals could be tuned by simply altering the precursor dosage and the NH₄F concentration. The photovoltaic tests show that with decreasing of particles size, the dye-sensitized solar cell (DSSC) exhibits lower open circuit voltage (V_oc) and fill factor (FF) due to the increased grain boundaries. However, because of the high short circuit current density (J_sc) stemming from the enhanced dye loading capacity, the power conversion efficiency (PCE) was promoted. Moreover, the shape effect on the DSSC performance was evaluated by comparing the nanocrystals with similar surface area but different shapes. The cell derived from truncated octahedrons exposing ∼25% {001} facets shows a ∼10% PCE improvement compared with the cell derived from octahedrons exposing ∼94% {101} facets. Based on the optical and recombination dynamic tests, the enhanced J_sc, V_oc and FF could be ascribed to the enhancement in light scattering effect and suppressed electron recombination, which may result from the improved connectivity of the adjacent nanoparticles because it is energetically favourable for the truncated octahedrons to be linked together by the high energy {001} facets.