Improving photochemical properties of Ipomea pescaprae, Imperata cylindrica (L.) Beauv, and Paspalum conjugatum Berg as photosensitizers for dye sensitized solar cells

This paper reports on the improving photochemical properties of natural dye using acid treatment, coadsorber addition, and dye combination. The natural pigments have been extracted from Ipomea pescaprae, Imperata cylindrica (L.) Beauv, and Paspalum conjugatum Berg containing quercetin 3-O-β-d-glucofuranoside, graminone B, and chlorophyll a. The dyes have been successfully sensitized on TiO₂ anatase nanoparticles as photoelectrodes for the dye-sensitized solar cell. The cells were illuminated under 100 mW/cm² AM 1.5 condition. It is investigated that the acidic treatments have been successfully improving the cell efficiencies of I. pescaprae dye from 0.45 to 0.53 %, I. cylindrica dye from 0.44 to 0.48 %, and P. conjugatum dye from 0.50 to 0.69 %. The acidic treatment leads to broaden the dye spectrum absorption and cell efficiency. Moreover, the addition of coadsorber into I. pescaprae dye is able to improve its cell efficiency from 0.53 to 0.55 % with J _sc of 3.738 mA/cm², V_oc of 0.393 V, and the FF of 0.377. The combination of dyes from I. pescaprae with efficiency of 0.27 % and P. conjugatum with efficiency of 0.55 % could be improved to be 0.76 %. In conclusion, we prove that the acidic treatment, coadsorber addition, and dyes combination play a significant role in improving the photochemical properties of natural dye sensitized solar cell.