Formation of efficient dye-sensitized solar cells by introducing an interfacial layer of long-range ordered mesoporous TiO₂ thin film

Long-range ordered cubic mesoporous TiO₂ films with 300 nm thickness were fabricated on fluorine-doped tin oxide (FTO) substrate by evaporation-induced self-assembly (EISA) process using F127 as a structure-directing agent. The prepared mesoporous TiO₂ film (MeSo-TiO₂) was applied as an interfacial layer between the nanocrystalline TiO₂ film (NC-TiO₂) and the FTO electrode in the dye-sensitized solar cell (DSSC). The introduction of MeSo-TiO ₂ increased J_SC from 12.3 to 14.5 mA/cm², and V_oc by 55 mV, whereas there was no appreciable change in the fill factor (FF). As a result, the photovoltaic conversion efficiency (η) was improved by 30.0% from 5.77% to 7.48%. Notably, introduction of MeSo-TiO ₂ increased the transmittance of visible light through the FTO glass by 23% as a result of its excellent antireflective role. Thus the increased transmittance was a key factor in enhancing the photovoltaic conversion efficiency. In addition, the presence of interfacial Meso-TiO₂ provided excellent adhesion between the FTO and main TiO₂ layer, and suppressed the back-transport reaction by blocking direct contact between the electrolyte and FTO electrode.