Efficiency enhancement in dye-sensitized solar cells by in situ passivation of the sensitized nanoporous electrode with Li2CO3

This work entails a method to improve the performance of dye-sensitized nanocrystalline TiO2 solar cells by adding surface passivating elements to the electrolyte. The presence of either CO2, Li2CO3 or K2CO3 in electrolyte increases both the photocurrent and the photovoltage, resulting in higher overall conversion efficiency of these solar cells. The additives are used to form a passivation layer of lithium carbonate on the dye free surface of the TiO2 nanoparticles and the conductive substrate. This layer suppresses the rate of the main recombination reaction between the photoinjected electrons and the oxidized ions in the electrolyte Solution. While blocking part of the recombination, the lithium carbonate layer allows motion of the Li+ ions towards the TiO2 surface for charge screening. Consequently using this simple treatment, the conversion efficiency of dye-sensitized solar cell most improved by 17.2% (from 6.4% to 7.5%). (C) 2008 Elsevier Ltd. All rights reserved.