In this work, two natural dyes extracted from henna and mallow plants with a maximum absorbance at 665 nm were studied and used as sensitizers in the fabrication of dye-sensitized solar cells (DSSCs). Fourier transform infrared (FTIR) spectra of the extract revealed the presence of anchoring groups and coloring constituents. Two different structures were prepared by chemical bath deposition (CBD) using zinc oxide (ZnO) layers to obtain ZnO nanowall (NW) or nanorod (NR) layers employed as a thin film at the photoanode side of the DSSC. The ZnO layers were annealed at different temperatures under various gas sources. Indeed, the forming gas (FG) (N₂/H₂ 95:5) was found to enhance the conductivity by a factor of 10³ compared to nitrogen (N₂) or oxygen (O₂) annealing gas. The NR width varied between 40 and 100 nm and the length from 500 to 1000 nm, depending on the growth time. The obtained NWs had a length of 850 nm. The properties of the developed ZnO NW and NR layers with different thicknesses and their effect on the photovoltaic parameters were studied. An internal coverage of the ZnO NWs was also applied by the deposition of a thin TiO₂ layer by reactive sputtering to improve the cell performance. The application of this layer increased the overall short circuit current J_sc by seven times from 2.45 × 10⁻³ mA/cm² to 1.70 × 10⁻² mA /cm².

Titanium dioxide (TiO2) thin film prepared by sol–gel technique and deposed by spin coating was used as the blocking layer between fluorine doped tin oxide and dyed TiO2 photoanode deposed by doctor blade in dye‐sensitised solar cell (DSSC). The synthesised films show a polycrystalline structure at annealing temperature of 400°C with small amount of amorphous phase observed at 300°C. The values of the electrical conductivity varies from 0.11 to 1.17 Ω ⁻¹ cm ⁻¹ for one and two layers thin films, respectively, and the corresponding activation energies decreased as a function of the thickness, it passes from 109 meV for one layer to 55 meV for two layers. The photoanode of the DSSC was sensitised by the mallow diluted in ethanol having absorption spectra with two peaks, one around 480 nm (blue light) and the second at 665 nm (red light) attributable to the chlorophyll mixture. Improvement of the electrical performance is due to the increased electron lifetime and decreased of the recombination process showed by the open circuit voltage decay measurement. The lifetime values increase from 0.80 ms for the cell without blocking layer to 1.24 ms for the cell based on the blocking layer.

Zinc oxide films doped with gallium (ZnG) were used as photoanodes in the dye sensitized solar cells (DSSCs). To enhance the electrical parameters of DSSC and decrease the recombination rate, a titanium dioxide (TiO₂) thin layer is inserted between a ZnG photoanode and substrate. Optical, structural, and morphological properties of films deposited on indium tin oxide coated on polyethylene naphthalate (ITO/PEN) and fluorine-doped tin oxide (FTO) substrates are studied. The realized films have a polycrystalline wurtzite hexagonal structure with the preferred orientation (002). By addition of gallium (Ga) to the ZnO solution, an improvement of the crystallinity is observed by increasing the grain size from 16.68 to 22 nm for the FTO/films and from 7 to 16.76 nm for ITO-PEN/films. The realized DSSCs show an increase of efficiency from 0.44% to 0.57% for DSSCs based on FTO and from 0.13% to 0.15% for ones based on ITO/PEN. The dyeing of the photoanodes by the natural mallow improves light absorption through the appearance of the absorbance regions in the range 665–680 nm. The doping of ZnO with Ga improves the open-circuit voltage of realized DSSC from 0.57 to 0.59 V for the DSSCs based on FTO and from 0.55 to 0.58 V for ones made on ITO/PEN.