CdS/CdSe co-sensitized vertically aligned anatase TiO2 nanowire arrays for efficient solar cells

The vertically aligned anatase TiO nanowire arrays with smooth or branched architectures were grown on TCO substrate directly via a simple surfactant-free hydrothermal route. And they were utilized to fabricate efficient quantum-dot sensitized solar cells (QDSSCs) for the first time. The thickness of CdS and CdSe shell were confirmed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-Ray spectroscopy (EDX). A power conversion efficiency of 4.2% was attained with the hierarchical TiO nanowires based cell, which is 30% higher than that of smooth nanowires devices due to improved short-circuit current density (J) and fill factor (FF). The increased J profits from superior light-scattering ability of branched hierarchical TiO nanowires for enhanced light-harvesting efficiency and the prominent charge-collection efficiency benefited from additional growth of branches for efficient and effective electron injection