Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO2 crystallisation

S. Guldin, S. Hüttner, P. Tiwana, M. C. Orilall, B. Ülgüt, M. Stefik, P. Docampo, M. Kolle, G. Divitini, C. Ducati, S. A. T. Redfern, H. J. Snaith, U. Wiesner, D. Eder*, U. Steiner*

Abstract

Anatase TiO2 is typically a central component in high performance dye-sensitised solar cells (DSCs). This study demonstrates the benefits of high temperature synthesised mesoporous titania for the performance of solid-state DSCs. In contrast to earlier methods, the high temperature stability of mesoporous titania is enabled by the self-assembly of the amphiphilic block copolymer polyisoprene-block-polyethylene oxide (PI-b -PEO) which compartmentalises TiO2 crystallisation, preventing the collapse of porosity at temperatures up to 700 °C. The systematic study of the temperature dependence on DSC performance reveals a parameter trade-off: high temperature annealed anatase consisted of larger crystallites and had a higher conductivity, but this came at the expense of a reduced specific surface area. While the reduction in specific surface areas was found to be detrimental for liquid-electrolyte DSC performance, solid-state DSCs benefitted from the increased anatase conductivity and exhibited a performance increase by a factor of three.