Significant influence of nano-SiO2 on the performance of dye-sensitized solar cells based on P25

Abstract

The present paper describes a new type of composite photo-anode of SiO2/TiO2 that was prepared by adding nano-sized SiO2 into the TiO2 (P25) paste during the fabrication of dye-sensitized solar cells (DSSCs). The effects of the added SiO2 on the performance of DSSCs were investigated and the preparative procedures of DSSCs were optimized. It was found that certain amount of SiO2 added in the P25 powder was crucial to reduce the agglomeration and enhance the dispersion of P25 powders, which helps to achieve a better connection and thus higher electron transfer efficiency not only between the TiO2 particles but also between the TiO2 particles and the FTO substrate. Under the same standard air mass 1.5 illumination (100mWcm−2), the DSSCs constructed by SiO2/P25 composite photo-anodes show higher solar energy-to-electricity conversion efficiency (e.g., η=8.4%) compared to those by bare P25 electrodes (typically η=5.8%). The higher η mainly results from its higher short-circuit photocurrent density (Jsc=18.7mAcm−2) while the open-circuit voltage (Voc) remains unchanged and was found to be ∼780mV. The fill factor (FF) was 0.57. The great enhancement in Jsc of DSSCs is ascribed to the SiO2 energy barrier layer which increases the separation of injected electrons and oxidized dyes/redox couple as well as retards the recombination reactions in the resulting DSSCs.