Light scattering management of dye-sensitized solar cells based on double-layered photoanodes aided by uniform TiO2 aggregates

•A new architecture of double-layered TiO2 electrodes is presented.•The electrode contains two alternate layers of TiO2 nanoparticles and aggregates.•The aggregates layers are deposited onto the nanocrystalline layer.•The new design showed improved efficiency compared to conventional cells.

This study presents a new double-layered TiO2 film containing a nanocrystalline under-layer and a uniform, sponge-like light scattering over-layer for dye-sensitized solar cells (DSCs) application. The over-layer is composed of 2-μm-diameter uniform aggregates, containing small nanoparticles with the average grain size of 20 nm. X-ray diffraction reveals that the light scattering layer has a mixture of anatase and rutile phases, whereas the nanocrystalline layer has a pure anatase phase. Ultraviolet–visible (UV–vis) spectra show that the light scattering layer has lower band gap energy than the nanocrystalline under-layer, extending the absorption of TiO2 into visible region. Diffuse reflectance spectroscopy demonstrates that the double-layered electrode enjoyed better light scattering ability. The double-layered DSC shows the highest power conversion efficiency of 7.69% and incident photon-to-current efficiency of 88% as a result of higher light harvesting and less recombination which is demonstrated by electrochemical impedance spectroscopy.

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