Efficiency Enhancement Achieved with Elongated Titania Nanocrystals for Dye Sensitized Solar Cells

Abstract

A significant efficiency enhancement of 28%, from 5.82 to 7.44%, is achieved by simply blending a minor amount of elongated titania nanocrystals to the photoanode of dye sensitized solar cells. With the addition of 10 wt % elongated titania nanocrystals of aspect ratio of 5, an increase of 24% in the short-circuit current density and a non-negligible increase of the open-circuit voltage from 0.71 to 0.74 V are obtained, leading to the observed efficiency enhancement. These improvements can be attributed to the enhanced light utilization and reduced electron-hole recombination, enabled by the extra light scattering and enhanced electron transport, respectively offered by the incorporated elongated titania nanocrystals. These nanocrystals are prepared at desired aspect ratios ranging from 1 to 5 with a template-free and surfactant-free hydrothermal process through adjusting the pH value of the reaction solution. This work demonstrates that the critical merits of enhancements in light scattering and electron transport can be realized through elongated titania nanocrystals, without the necessity of using nanowires, nanotubes, or nanorods of high aspect ratios.