Development of an aqueous TiO₂ paste in terms of morphological manipulation of nanostructured photoanode electrode of dye-sensitized solar cells

A novel simple synthetic procedure for improving cell efficiency and reducing the production cost of TiO₂ dye-sensitized solar cells (DSSCs) by modification and optimization of homemade formulated paste is reported. This is achieved in terms of morphological manipulation of deposited monolayer TiO₂ films by controlling three processing parameters of paste formulation. These parameters are tailored to obtain a paste with proper viscosity suitable for spin-coating technique and to achieve uniform, homogeneous, and crack-free films with good connections between TiO₂ grains and porous structure. Photovoltaic measurements show that TiO₂ monolayer DSSC fabricated from the optimized paste formulation (i.e., T7B5G12) has the highest power conversion efficiency (PCE) and short-circuit current (J _SC) of 5.36 ± 0.04 % and 14.29 ± 0.02 mA/cm², respectively. The double-layer DSSCs are also fabricated to enhance electron transport rate and light scattering of the cells. These cells are composed of T7B5G12 film as the under-layer and mixtures of various morphologies (i.e., nanoparticles, regular nanowires, corn-like nanowires, and microparticles) as the over-layers. An enhancement of PCE and J _SC up to 7.05 ± 0.024 % and 16.67 ± 0.04 mA/cm², respectively, is achieved for double-layer DSSC containing a mixture of nanoparticles and corn-like nanowires, as the over-layer. The photovoltaic improvement of double-layer cells is related to tailoring the light scattering, photogenerated charge carriers, and dye-loading parameters.