Dye-sensitized solar cells (DSSC) were fabricated using red Bougainvillea glabra flower dye extracts as natural dye sensitizers at three dye pH values of 1.23, 3.0 and 5.7. Water was used as dye extracting solvent. Dye-sensitized solar cells (DSSCs) from dye extract of pH 3.0 had the highest photocurrent density J of 3.72 mA/cm2 and fill factor FF of 0.59. While the DSSCs from dye sensitizer pHs of 1.23 and 5.7 had Jsc of 1.13 mA/cm2 and 2.27 mA/cm2, and fill factors of 0.43 and 0.61 respectively. The maximum powers Pmax of the DSSCs were 0.50, 1.64 and 0.94 mW/cm2 for dye sensitizer pH of 1.23, 3.0 and 5.7 respectively.

Dye-sensitized solar cells (DSSC) were fabricated using red bougainvillea glabra flower dye extracts as natural dye sensitizers at three dye pH values of 1.23, 3.0, and 5.7. Water was used as dye-extracting solvent. DSSCs from dye extract of pH 3.0 had the highest photocurrent density J sc of 3.72 mA/cm 2 and fill factor FF of 0.59. While the DSSCs from dye sensitizer pHs of 1.23 and 5.7 had J sc of 1.13 and 2.27 mA/cm 2 , and fill factors of 0.43 and 0.61, respectively. The maximum powers P max of the DSSCs were 0.50, 1.64, and 0.94 mW/cm 2 for dye sensitizer pH of 1.2, 3.0, and 5.7, respectively.

Dye-sensitized solar cells (DSSCs) comprising mesoporous TiO 2 films and betalain pigments extracted from red Bougainvillea glabra flower as natural dye sensitizers were fabricated and enhanced by the intercalation of the plasmonic silver nanoparticles (Ag NPs) into the pores of mesoporous TiO 2 electrodes by successive ionic layer adsorption and reaction (SILAR) method. The TiO 2 / Ag NPs composite films were characterized by SEM and UV-Vis spectroscopy. I-V characteristics of the devices were measured by solar simulator (AM1.5 at 100 mW/ cm 2 ). The incorporation of the Ag nanoparticles into the pores of mesoporous TiO 2 electrodes with one SILAR deposition cycle of the Ag NPs produced the best plasmonic enhanced-DSSC giving a short-circuit current density (J sc ), fill factor (FF), and power conversion efficiency (PCE) of 1.01 mA cm -2 , 0.77, and 0.27 %, respectively. This development amounts to 50 % efficiency enhancement over the reference DSSC that had a short-circuit current density (J sc ), fill factor (FF), and power conversion efficiency (PCE) of 0.7 mA cm -2 , 0.57, and 0.18 %, respectively.

This research is focused on the design and implementation of a microcontroller based electrostatic spray pyrolysis instrument that can sense and regulate temperature change with an alternating current to direct current converter in the range of 220V-1KV AC to 20KV DC for thin film deposition. In spray pyrolysis technique precise management of the spray parameters helps to create good and uniform thin films with ease of reproducibility of film properties. However it is a draw back in the manually operated electrostatic spray pyrolysis instrument mostly used in developing countries of Africa which causes variations in film structure, thickness, associated film properties and difficulty of reproducibility of film properties. The need for improved locally made ESP unit is also timely due to the inadequacy/unavailability of thin film deposition apparatus in most African institutions/materials research laboratories. The circuit was simulated on Multism software and transfer to PCB, etching was done using Lead (II) oxide while the unit components where assembled by soldering of electronics components, bonding and drilling of associated components. Arduinounoatmega 328 micro controller was employed. The fabricated device operated at 1KV to 20KV dc voltage for film deposition, at a substrate temperature range of 100oC to 450oC with a steady flow rate of 0.04ml/min, define spray pattern, define precursor usage and a precise control of major deposition parameters. ZnO:Al thin film deposited with the equipment was found to have a crystalline structure of fine grains.  Â

In this work we have reported an investigation on Hibiscus sabdariffa and Delonix regia dye extracts and their mixture as natural sensitizers for TiO2/DSCs. A shift in the absorption maximum toward the lower energy of the ultraviolet-visible spectrum was observed for the dye mixture and a shift in the absorption maximum towards the higher energy of the ultraviolet-visible spectrum was observed for the dye extracts. The optical band gaps obtained at the point where the absorption spectra showed strong cut offs range from 1.79eV to 2.40eV. Also, we have used TiO2 thin films of thickness 5.2μm and the Light Harvesting Efficiencies (LHE) of the dye extracts and the dye mixture adsorbed onto TiO2 surface were close to unity. The average diameter of the TiO2 films obtained from SEM is in the range of 25-40nm reflecting that the TiO2 films are transparent and suitable for DSC application. The XRD pattern revealed the TiO2 films to be of anatase form and the structure type is tetragonal with 3.53217Å as the d-spacing for the most prominent peak, 2θ=25.2139° (ICDD data file: 01-075-8897). Three (3) DSCs each of 0.52 cm2 active area were assembled and subjected to current-voltage characterization using a standard overhead Veeco viewpoint solar simulator equipped with AM 1.5 filter to give a solar radiation of 1000 W/m2 and coupled to Keithley source meter (model 4200SCS). The photoelectrochemical performance of the fabricated DSCs showed open-circuit voltages (Voc) varied from 0.42 to 0.53 V, the short-circuit current densities (Jsc) ranged from 0.10mAcm-2 to 0.90mAcm-2 and the fill factors (FF) varied from 12 to 38%. The best overall solar power conversion efficiency of 0.13% was obtained, under AM 1.5 irradiation and a maximum short circuit current density of 0.90mAcm-2. Nevertheless, pure Hibiscus sabdariffa and Delonix regia dye extracts proved to be rather poor sensitizers as can be seen by the low spectra absorption at lower energies with current densities of 0.17mAcm-2 and 0.10mAcm-2 respectively. The solar power conversion efficiencies for Hibiscus sabdariffa and Delonix regia dye extracts were 0.01% and 0.02% respectively. In our earlier studies, we highlighted an established fact that raw natural dye mixtures exhibit better performance than pure dye extracts. Thus, the power conversion efficiency of 0.13% observed for the dye mixture sensitized TiO2/DSC corresponds to an increment in the neighborhood of 85% to 92% over the pure dye extracts sensitized TiO2/DSCs.