Preparation and photoelectrochemical properties of TiO2 hollow spheres embedded TiO2/CdS photoanodes for quantum-dot-sensitized solar cells

Abstract

A novel process was developed by introducing TiO2 hollow spheres (THS) into TiO2 nanoparticles film as light scattering centers to improve the light harvesting of CdS sensitized TiO2 (TiO2/CdS) photoanodes for quantum-dot-sensitized solar cells (QDSCs). The THS in TiO2 nanoparticles film can largely enhance the light scattering due to the multi-reflection among or within the THS, leading to the increase of optical path length in TiO2 film. Furthermore, the THS in TiO2 particles favors the penetration of CdS nanocrystals in the porous TiO2 film. As a result, the photocurrent is significantly improved with THS embedding in TiO2/CdS photoanodes. The experiment results suggest that an optimal content of THS is highly desired, too high content of THS in the photoanode will degrade the light to electricity conversion efficiency due to the strong back-scattering in the interfacial area of TiO2 film and the conducting glass, penetration of excess and large CdS nanocrystals, and poor charge transfer between TiO2 particles. The photoelectrochemical measurement shows that the highest photocurrent of 2.4mA/cm2 was obtained with 10% THS in the TiO2/CdS photoanode, which is nearly four times higher than that of the TiO2/CdS photoanode without THS (0.5mA/cm2).