Effect of zinc oxide quantum dots on the photovoltaic properties of natural dye-sensitized solar cells

Natural dyes are used as solar-sensitive materials to construct environmentally friendly solar cells. The low efficiency of natural dyes is one of their limitations in solar cells. To solve this problem, zinc oxide quantum dots have been used as an improving agent in the development of environmentally friendly solar cells. In the current study, natural dyes were extracted from Cytisus, Alcea rosea, and Roselle flowers using the solvent method. Then, the zinc oxide quantum dots (ZnO QDs) were synthesized through co-precipitation in ethanol solutions. Subsequently, dye-sensitized solar cells (DSSC) were made using the extracted dyes, and zinc oxide quantum dots were used to enhance the efficiency of the solar cells. Ultraviolet-visible (UV-Vis) spectrophotometry and Fourier transform infrared (FTIR) spectroscopy were used to study the absorption spectra of the extracted dyes and their functional groups. X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), and photoluminescence (PL) methods were used to characterize the crystal structure, size, particle size distribution, and emission intensity of the synthesized quantum dots, respectively. TEM, DLS, and PL analyses showed that the particle size of the quantum dots in the optimized sample was about 3 nm, and the maximum emission intensity was equal to 1550 at 520 nm. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS) were used to determine glass, fluorine-doped tin oxide (FTO), TiO2, ZnO QDs, and dye layers separately. Electrochemical impedance spectroscopy (EIS) was used to evaluate the resistance of solar cells. The properties of the modified solar cells were also investigated using the photovoltaic and incident photon to current conversion efficiency (IPCE) methods. The efficiency of the solar cell was equal to 0.983% with an open-circuit voltage (V-oc) of 0.648 (V), short-circuit current (J(sc)) of 2.251 (mA/cm(2)), fill factor (FF) of 0.647, and IPCE value of 21.662%. The results indicated that the modified solar cells performed better than the unmodified cells, and the use of quantum dots increased the efficiency of environmentally friendly solar cells by 17%.