Namita Singh, Sahiba Siddiqui, Namrata Ghildiyal
Abstract Dye-sensitized solar cells (DSSCs) are popular due to their use in renewable energy generation. They convert sunlight into electricity with the help of natural pigments. Natural dyes like anthocyanins, carotenoids, chlorophyll and betalains are easily extracted from vegetables, fruits and flowers present in nature and contribute to green and sustainable solar energy harvesting when immobilised on the TiO2 surface of the photoanode of DSSCs. These natural pigments help in light absorption and act as electron carriers to the conduction band gap of the semiconductor metal oxide in dye-sensitized solar cells. The photosensitization process can be tracked by UV-visible spectroscopy. The FTIR spectra of dyes immobilized on titania film is a contribution of interactions amongst different anchoring groups of photosensitiser molecules on the TiO2 surface. This review compiles the data of past and recent investigations on TiO2 nanoparticle-based dye-sensitized solar cells (DSSCs) utilizing blends of extracts prepared from fruits, vegetables and flowers. The light-harvesting efficiency of blends was correlated to spectral variations observed in the UV-visible absorption spectra of the dyes present in blends adsorbed on a TiO2 layer. Blends that showed good conversion efficiency were identified from the study. The factors affecting the efficiencies of the blends and solo pigments are also reported. DSSCs are cheap and flexible to use under both indoor and outdoor conditions. The pigments are bio-compatible in nature, non-hazardous and inexpensive. They can aid in the conversion of biomass to solar energy and attach value to fruit, flower and vegetable wastes.