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 (JSC) 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 JSC 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. Graphical Abstract: [Figure not available: see fulltext.]