Influence of anthocyanin co-pigment on electron transport and performance in black rice dye-sensitized solar cell

Abstract

This work reports the novel contribution of chlorophyll b as natural anthocyanin co-pigment in unpurified black rice extract for improved electron transport and performance of natural dye-sensitized solar cell. The dyes are extracted as prominent photosensitizers by considering the concentration, the dye electronic structure, the extraction, and immersion time. The anthocyanin dye containing 1.92 mM cyanidin-3-O-glucoside structure has been extracted without purification. Interestingly, 0.33 mM chlorophyll b is found as a natural co-sensitizer in unpurified anthocyanin. The role of chlorophyll b supporting the electron transfer of anthocyanin dye will be investigated for improved cell performance. Both purified and unpurified dyes are compared in the same anthocyanin concentration. The combined Tauc plot and voltametric method will be conducted to show the interfacial electronic band edges of TiO2-dye-electrolyte. Electrochemical impedance spectroscopy method will investigate electron transfer dynamic in both cell systems. As a result, chlorophyll b has dominantly acted as two intermediate states in boosting electron injection and dye regeneration to improve cell efficiency from 1.31 to 2.17 % due to the narrower LUMO–TiO2 conduction band gap and the narrower HOMO-iodide (I −) potential gap, respectively. According to the electron transport, the co-sensitizer contributes to the smaller transport resistance (R t = 21.9 Ω), the higher chemical diffusion coefficient (Dn = 1.696 × 10−3 cm2/s), the higher chemical capacitance (Cμ = 14.32 μF), and the faster electron transport (τd = 39.88 μs).