Natural dye production for use in dye sensitized solar cells

Nowadays, when fossil fuels are starting to run out and environmental problems are increasing, renewable energy technologies are so crucial. Accordingly, one of the most basic sources of renewable energy is sun and photovoltaic cells (PV) that are used to convert solar energy into electricity are being developed rapidly. Dye sensitized solar cells (DSSCs) are the most sought-after systems due to their environmental friendliness and low cost. In this study, four different alternative natural dye sources were studied comparatively for dye sensitizers which are one of the key elements of DSSCs. Blackberries (Rubus fructicosus), black mulberries (Morus nigra), wild cherries (Prunus serotina) and raspberries (Rubus ideaus) were subjected to extraction at 40 ° C for 60 minutes in an ultrasonic bath after pretreatment. The natural dye extracts obtained after the process were vacuum filtered and centrifuged to remove the fruit particles. Five different pH values (1-2-3-4-4,5) were studied in order to determine which pH is richer in terms of anthocyanins, one of the most important natural pigments giving red color. The dyes prepared were analyzed by UV-VIS Spectrophotometer and the natural dye extracts were compared both in terms of pH and in terms of their pigment densities. It was found that the maximum absorption of the anthocyanins for each dye was at pH 1 at 520 nm. According to the pigment densities, the natural dyes can be ordered as wild cherries, blackberries, black raspberries and raspberries, respectively. At the same time, structural characterization of natural dyes was also analyzed by FT-IR and Raman spectroscopy. In order to examine the coloring of the natural dyes on the TiO2 semiconducting surface in DSSC systems and fading under sunlight, a transparent glass coated with F-doped tin oxide (FTO) and TiO2 mixture was prepared. The FTO glass was coated with TiO2 and the TiO2 portion of the coated glass was left in the four different natural dyes at pH 1 for 24 hours. According to the coloring characteristics, the natural dyes are lined up wild cherry, blackberry, black mulberry and raspberry, respectively. Since black mulberry and raspberry are very low in color, they stay on the TiO2 surface for about 2 month, while wild cherries and blackberries can stay for about 4 months. Consequently, wild cherry gives the best results in terms of the properties examined among the four fruits and is a promising material as a dye sensitizer in DSSC systems.