SnO2 has high electron mobility and low photocatalytic action compared to TiO2. However, SnO2-based DSCs have shown limited performance due to their high electron recombination. Recombination can be suppressed to a certain extent using Li+ as an electron screening layer on the SnO2 surface. Li+ ions are adsorbed on to the SnO2 surface as the surface is negatively charged by O2- sites and -OH groups. This will shift the conduction band edge of SnO2 towards more positive direction thus increasing the electron harvesting efficiency of the device. Also, recombination occurring at the FTO/electrolyte interface can be reduced using tert-butylpyridine (TBP) as a gel electrolyte-additive as it covers the uncovered FTO surface. The gel electrolyte showed 4.7 x 10-3 S cm-1 of ionic conductivity and 4.91 x 10-6 cm2 s-1 of diffusivity for triiodide ions. These values agreed with the reported values in literature. In this study, the DSCs were fabricated with the device structure of FTO/Li+-doped SnO2/D358 dye/gel electrolyte/lightly platinized FTO counter electrode. The device containing 1:0.06 molar ratio of SnO2 to Li+ gave an efficiency of 4.3% while undoped device gave 1.6%. Li+-doped system showed 30% increase in current density and 61% increase in VOC.
Wanninayake, W. M. N. M. B., Premaratne, K., & Rajapakse, R. M. G. (2016). Investigation of the Effects of Li+-doping on the Photovoltaic Performance of SnO2-based Quasi-Solid-State Dye-Sensitized Solar Cells. In Procedia Engineering (Vol. 139, pp. 69–75). Elsevier Ltd. https://doi.org/10.1016/j.proeng.2015.09.221