Charge Transfer Dynamics of Highly Efficient Cyanidin-3-O- Glucoside Sensitizer for Dye-Sensitized Solar Cells

This paper reports the novel efficiency achievement of black rice-based natural dye- sensitized solar cells. The higher dye concentration, the longer dye extraction as well as dye immersion onto a TiO₂ film, and the co-adsorption addition are key strategies for improved-cell performance compared to the highest previous achievement. The black rice dye containing 1.38 mM cyanidin-3-O-glucoside has been extracted without purification for 3 weeks at dark condition and room temperature. The anatase TiO₂ photoanode was dipped into dye solution within 4 days. Its electrode was firmly sealed to be a cell and was filled by I^-/I³- electrolyte using vacuum technique. As a result, the overall solar-to-energy conversion efficiency was 1.49% at AM 1.5 illumination (100 mW.cm^-2). The voltametric analysis has reported the interfacial electronic band edges of TiO²-Dye-Electrolyte. Furthermore, electrochemical impedance spectroscopy has shown the kinetic of interfacial electron transfer dynamics among TiO²-dye-electrolyte. The cell has the transfer resistance (Rt) of 12.5 ω, the recombination resistance (Rr) of 266.8 ω, effective electron diffusion coefficients (Dn) of 1.4 × 10^-3 cm²/s, Dye-TiO₂ effective electron transfer (τ_d) of 26.6 μs, effective diffusion length (L_n)of 33.78 μm, chemical capacitance (C_μ) of 12.43 μF, and electron lifetime (τ_n) of 3.32 ms.