We report on the use of natural dyes, betalains, as pigments for Dye-Sensitized Solar Cells (DSSC). Time-Dependent Density Functional Theory calculations provide the electronic spectra of the various types of betalain dyes and allow a discussion of their matching to the solar spectrum. Experimentally, we vary parameters such as the nature of the extracting solvent, the pH and the composition of the extract, to optimize the fabrication of DSSCs using betalains. Based on UV-Vis spectra correlated with electro-optic measurements providing the photovolatic conversion efficiency under standard AM1.5 conditions we find that the decrease of the pH of the dye solution leads to an increase of the DSSC performance, likely due to the increasing ratios of betacyanins with respect to betaxanthins in the extracts as well as the possible hydrolysis of betanin to betanidin. In order to fabricate better DSSCs using betalain natural dyes, we propose to use water as extracting solvent, to increase the content in betacyanins on the photoanode by a preliminary purification and to raise the stability of the dyes preferably by using anti-oxidizing copigments that do not interact with the substrate
