Biological Synthesis of ZnO Nanoparticles Using Fruit Extract of <i>Ruta Chalepensis</i> as Photolectrode for Dye Sensitized Solar Cell Application

Abstract Currently energy crisis is one of the challenging issues worldwide. As such, generation of green alternative energy should take the attention of researchers around the globe. This work reports synthesis of zinc oxide nanoparticles (ZnO NPs) using biological method (using fruit extract of Ruta chalepensis ) for photoanode of dye sensitized solar cells (DSSCs). In the study, the performance of DSSCs derived from chemically synthesized and biologically synthesized ZnO NPs were evaluated. The plant extract templated synthesis of ZnO NPs were prepared in varied zinc nitrate to R. chalepensis fruit extract ratios of 1 : 2,1 : 1, and 2 : 1 and labeled as g‐ZnO(1 : 2), g‐ZnO(1 : 1) and g‐ZnO(2 : 1); and that of chemically synthesized ZnO NPs is labelled as c‐ZnO (as a control). Thermogravimetric analysis‐differential thermal analysis (TGA/DTA) reveals that ZnO NPs are stable above 450 °C. From X‐ray diffraction (XRD) pattern, average size of g‐ZnO(1 : 2), g‐ZnO(1 : 1), g‐ZnO(2 : 1) and c‐ZnO NPs were estimated to be 7, 13, 18 and 26 nm, respectively. Scanning electron microscopy (SEM) reveals the presence of ZnO in clustered, flake‐like, and some agglomerated spherical forms; and energy dispersive spectroscopy (EDX) confirms presence of Zn and O atoms in the sample. The optical band gaps of g‐ZnO (1 : 2), g‐ZnO(1 : 1), g‐ZnO(2 : 1) and c‐ZnO NPs were measured to be 3.30, 3.25, 3.23 and 3.22 eV respectively using ultraviolet‐visible (UV‐Vis) absorbance spectrophotometer. Fourier transform infrared (FT‐IR) spectroscopic analysis shows the absorption band for Zn−O bonding between 400 and 600 cm −1 . The produced photoanode, crystal violet dye, quasi‐solid‐state electrolyte, and counter electrode were used to fabricate DSSCs. The power conversion efficiency (PCE) of the constructed DSSC device with a c‐ZnO photoanode is 1.95 %, and those with a g‐ZnO (2 : 1), g‐ZnO(1 : 1), and g‐ZnO(1 : 2) photoanodes have PCE of 1.9 %, 1.36 %, and 0.215 % respectively.