Energy band tunable TixSn1−xO2 photoanode for efficient non-TiO2 type dye sensitized solar cells

Abstract

Ti_xSn_1−xO₂ (x = 6–70%) solid solution nanoparticles with tunable energy band structures are prepared for dye sensitized solar cells (DSSCs). It is found that the energy band gap of Ti_xSn_1−xO₂ (x = 6–10%) is larger than that for SnO₂, which is beneficial for the long term stability of DSSCs. They are also efficient in reducing the interfacial recombination in DSSCs with sensitizer N719. DSSCs with a transparent Ti_10%Sn_90%O₂ photoanode achieve the highest energy conversion efficiency of 3.67% (1 sun, AM1.5) among Ti_xSn_1−xO₂ (x = 6–70%) photoanodes, nearly three times higher than that with a pure SnO₂ photoanode (1.37%). However, Ti_xSn_1−xO₂ with a large Ti content (15–70%) becomes photoactive and reduces the electron transport in DSSCs. The photoactivity of the photoanodes and the varied performances of the DSSCs are explained well by the energy band structure of Ti_xSn_1−xO₂ (x = 6–70%), as well as the SnO₂ and TiO₂ photoanodes. With an SnO₂ light scattering layer and a thin MgO coating on a Ti_6%Sn_94%O₂ photoanode, the performance of the DSSC reaches 5.24% (photocurrent density J_sc = 10.3 mA cm⁻², open circuit voltage V_oc = 0.732 V and fill factor FF = 0.695), which is an efficient non-TiO₂ type photoanode for DSSCs.