Extraction, characterization and energy investigation of Garcinia kola, Cola Nitida and Cola Accuminata for efficient light absorption in dye-sensitized solar cells

Natural extracts were obtained from the Garcinia kola, Cola Nitida and Cola Accuminata. The extracts from Garcinia kola, Cola Nitida and Cola Accuminata were evaluated for their phytochemical, electrochemical and photovoltaic current–voltage (I-V) light-to-electricity conversion efficiency in dye-sensitized solar cells (DSSCs). This is the first time when flavonoid, garcinoic, caffeine and their derivatives from the Garcinia species will be tested for electrochemistry and for DSSCs power conversion efficiency. The results revealed that the different affinity among the three Garcinia sp.; Cola Nitida, Cola Accuminata and Garcinia kola with TiO₂ semiconductor was responsible for their various adsorption, binding and light absorption transfer into the semiconductor band edge. Cyclic voltammetry of the three compounds shows a well-defined redox nature, good reversibility of electron transfer and dye regeneration. Cola Nitida NIT compound had the lowest Homo energy level (-5.130 eV) and highest Lumo energy value (-2.029 eV) than Garcinia kola and Cola Accuminata. GK compound revealed lower-charge transfer resistance than ACC and NIT. Gk sensitizer showed an improve light-to-electricity conversion efficiency (η₂) = 0.14 %, FF = 0.753, V_oc = 0.850 V and J_sc = 0.200 mAcm⁻² under 1 sun illumination giving a standard deviation efficiency of 0.024 as compared to ACC and NIT.