Chemical sintering by chlorinated carbon compounds for flexible photoanodes of dye-sensitized photovoltaic cells

Novel binary solvent mixtures of chlorinated carbon compounds (CCs = CCl₄, CHCl₃, and C₂Cl₄) and 1-octanol are used to prepare pastes of TiO₂ nanoparticles (NPs), which facilitate the formation of stable and thick TiO₂ mesoporous films for photoanodes of dye-sensitized solar cells (DSSCs). CCs and 1-octanol readily form a complex, leading to enhanced interparticle connectivity within TiO₂ NPs through hydrogen bonding interactions. The as-prepared chemically sintered TiO₂ films exhibit high porosity and homogeneity, and a strong interparticle network for improved mechanical stability. The highest power conversion efficiency (PCE) of 7.0 and 5.8% is achieved using C₂Cl₄ for fluorine-doped tin oxide (FTO)-based rigid-type DSSCs and flexible-photoanode (indium-doped tin oxide (ITO)-coated polyethylene naphthalate (ITO/PEN))-based DSSCs, respectively, under 1-sun illumination conditions. Furthermore, the optimized device exhibits a significantly high PCE of 19.9% under indoor low-intensity light conditions.