Toward a Quantitative Correlation between Microstructure and DSSC Efficiency: A Case Study of TiO_2–<i>x</i>N_<i>x</i> Nanoparticles in a Disordered Mesoporous Framework

Abstract

The efficiency (η) of a dye-sensitized solar cell (DSSC) depends on various parameters, the critical factors being a fast charge carrier transport and a slow rate of electron–hole recombination. The present article describes a simple combustion synthesis method to prepare TiO2–xNx with following four important features that directly influences η: (1) a disordered mesoporous structural framework with high surface area to give high dye-loading and a small diffusion length for charge carriers allowing rapid movement to the surface; (2) electrically interconnected nanocrystalline TiO2–xNx particles with good necking and predominant (101) anatase facets to minimize electron–hole recombination; (3) low charge storage capacity in the titania framework; and (4) surface unsaturation assisting all the above factors. The pseudo-three-dimensional nature of mesoporous TiO2–xNx with the above features demonstrates the importance of textural features, and porosity allows faster diffusion of charge carriers to surface and their utilization to generate power. A quantitative correlation between interconnected nanoparticles over larger distances in a mesoporous framework and η is demonstrated. This study also demonstrates an inexpensive and rapid method of producing the photoanode material with high η in about 10 min.