Dye-sensitized solar cells with natural dyes extracted from achiote seeds

We have explored the application of natural dyes extracted from the seeds of the achiote shrub (Bixa orellana L.) in dye-sensitized solar cells (DSCs). The main pigments are bixin and norbixin, which were obtained by separation and purification from the dark-red extract (annatto). The dyes were characterized using 1H-NMR, FTIR spectroscopy, and UV–Vis spectrophotometry. Solar cells were prepared using TiO2 and ZnO nanostructured, mesoporous films and the annatto, bixin, and norbixin as sensitizers. The best results were obtained with bixin-sensitized TiO2 solar cells with efficiencies of up to 0.53%, illustrating the importance of purification of dyes from natural extracts.