Efficient monolithic dye sensitized solar cells with eco-friendly silica-titania spacer layers

Monolithic assembly of dye-sensitized solar cells (M−DSSCs) is technologically attractive due to its ease of fabrication, compactness and lower production cost. However, combining cost-effective materials with high power conversion efficiency in M−DSSCs is still a challenging task. New silica–based spacer layers for M−DSSCs, derived from entirely water-based paste formulation were developed. A commercial aqueous suspension of SiO₂ nanoparticles (LUDOX-40), modified with hydroxypropyl cellulose as a binder, were used for formulating the silica paste. The reflectance of the spacer layers was tuned by adding anatase nanoparticles; when 30 wt% of titania was added to the SiO₂-TiO₂ composite, a sharp increase of the reflectivity of the spacer layers was observed rendering a device with the highest to date reported power conversion efficiency of 8.3% and full stability. The effect of titania concentration in the SiO₂ spacer layer on the photovoltaic performance, the spectral response of the photocurrent and recombination in M−DSSCs is discussed.