All-solid-state dye-sensitized solar cells with high efficiency

Abstract

Dye-sensitized solar cells based on titanium dioxide (TiO₂) are promising low-cost alternatives to conventional solid-state photovoltaic devices based on materials such as Si, CdTe and CuIn_1−xGa_xSe₂ (refs 1, 2). Despite offering relatively high conversion efficiencies for solar energy, typical dye-sensitized solar cells suffer from durability problems that result from their use of organic liquid electrolytes containing the iodide/tri-iodide redox couple, which causes serious problems such as electrode corrosion and electrolyte leakage³. Replacements for iodine-based liquid electrolytes have been extensively studied, but the efficiencies of the resulting devices remain low^{3,4,5,6,7,8,9}. Here we show that the solution-processable p-type direct bandgap semiconductor CsSnI₃ can be used for hole conduction in lieu of a liquid electrolyte. The resulting solid-state dye-sensitized solar cells consist of CsSnI_2.95F_0.05 doped with SnF₂, nanoporous TiO₂ and the dye N719, and show conversion efficiencies of up to 10.2 per cent (8.51 per cent with a mask). With a bandgap of 1.3 electronvolts, CsSnI₃ enhances visible light absorption on the red side of the spectrum to outperform the typical dye-sensitized solar cells in this spectral region.