ORAC and VIS spectroscopy as a guideline for unmodified red–purple natural dyes selection in dye-sensitized solar cells

•ORAC and UV–Vis spectra can be used for conversion efficiency indicator of DSSCs.•Natural dyes were extracted by simple methods without further modifications.•No special treatment was made on working electrode or any other parts of the DSSCs.

Red–purple natural sensitizers are prepared from anthocyanins and betalains rich section of plants which are extracted by simple methods without further modifications such as commercial juice (Welch grape juice) and juices obtained by fresh squeezing or hot water extraction. No special treatments on the surface of TiO2 electrode has been made to enhance the adhesion between natural dye and TiO2. An outstandingly high power conversion efficiency (η) of DSSCs are obtained from purple yam (2.05%), pomegranate (1.35%) and Welch grape juice (0.82%). ORAC (Oxygen Radical Absorbing Capacity) and VIS spectroscopy data can be used as a guideline for the conversion efficiency indicator of DSSCs using anthocyanins (without tannins) dyes. On the contrary, only ORAC can be used as a guideline for the conversion efficiency indicator of DSSCs in the case of anthocyanins (with tannins) dyes.