Simple development of eco-friendly dye-sensitized solar cells via controlling thickness of TiO2 nanoparticles and viscosity of electrolyte: Experimental study and DFT calculations

The pigments (N-3 dye, anthocyanin, and oleandrin) that absorb light in the visible region, change electrolyte viscosity KI/I2 by adding polyethylene glycol (PEG), and the painting method of TiO2 using the spray and doctor-blade methods was studied. The ultraviolet-visible (UV-VIS) spectra of natural dyes showed strong bands in the visible regions at 350-450 nm. The Fourier-transform infrared (FTIR) spectra confirmed the formation of the N3-triodide complex which was not observed for the other natural dyes. The impact of the changing of viscosity by the addition of PEG improved the current flow in dye-sensitive solar cells (DSSCs). Scanning electron microscopy (SEM) images showed a homogenous and thin film of TiO2 by using the spray method. The efficiency of N-3-DSSCs jumped and reached 0.2770% by the sprayed method in PEG-KI/I2 electrolyte. The efficiencies of 0.195 and 0.089 % for BB and NO-DSSCs were recorded in PEG-KI/I2 electrolytes, respectively. A low-cost carbon counter electrode was used in fabricating for DSSCs. The reduction in the values of RSH (shunt resistance) had a negative impact on the performance of DSSCs. Density functional theory (DFT) calculations were studied for optimized geometry of the three dyes. The chemical potential mu of N-3 was greater than that of anthocyanin, and oleandrin which reflects the ability of electrons to exchange with TiO2. The Eg (energy gap) of N-3 got to a height that slowed the rate of recombination of electron-hole of dye. The electronic chemical potential (mu) and energy gap (Eg) are effective to improve the efficiency of DSSCs.