Yuly Kusumawati : Charge Transport and Recombination in TiO2 Brookite-based Photoelectrodes
Yuly Kusumawati S.Si, M.Si
The Journal of Physical Chemistry C
The photoactivity of the stable nano-sized TiO2 polymorphs is challenging for many advanced applications. In the present work, brookite TiO2 nanoparticles with two different shapes have been used as building blocks for the preparation of pure brookite porous layers. The layer structure and dye sensitization have been characterized. They have been used as photoanodes in dye-sensitized solar cells (DSSCs). The cell functioning coupled processes have been investigated by the impedance spectroscopy (IS) technique at various applied voltages and compared to a reference anatase TiO2 solar cell. From the analysis of the impedance spectra, the trap state distributions have been determined and shown to explain the observed variations of solar cell open circuit voltage, Voc. The investigations of the charge transfer reaction and charge carrier transport show that, compared to anatase, the brookite surface is less active for the recombination reaction. However, the charge transport is much slower in the brookite phase due to a lower electrical conductivity. This parameter has been quantified more than one order of magnitude lower in the brookite layers compared to the anatase one. On the whole, the efficiency of brookite DSSCs is mainly limited by two parameters, the dye loading and the charge collection efficiency.