Transport and interfacial transfer of electrons in dye-sensitized solar cells based on a TiO2 nanoparticle/TiO2 nanowire “double-layer” working electrode

Dye-sensitized solar cells (DSSCs) with different thickness TiO2 nanoparticle films and a “double-layer” working electrode of TiO2 nanoparticle/TiO2 nanowire are fabricated. The influence of the TiO2 nanoparticle films thickness and of a light-scattering layer of TiO2 nanowire on the photovoltaic performance of DSSCs are investigated. The transport and interfacial transfer of electrons in DSSCs are investigated using intensity modulated photocurrent spectroscopy (IMPS), intensity modulated photovoltage spectroscopy (IMVS), and electrochemical impedance spectroscopy (EIS) to determine the lifetime, diffusion coefficient, and diffusion length of the electrons. The results indicate that the optimum TiO2 nanoparticle films' thickness for DSSCs is about 14 μm. The introduction of the light-scattering layer leads to an obvious enhancement of the power conversion efficiency. This can mainly be attributed to the superior light-scattering ability, fast electron transport, and long electron lifetime, resulting in a larger electron diffusion coefficient and a higher charge collection efficiency, which are confirmed by IMPS, IMVS, and EIS.