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The efficiency of Dye-Sensitized Solar Cells (DSSC) can be significantly enhanced by optimizing the concentration of surface trap states and by tailoring the band gap energy in the semiconductor oxides used as photoanodes. Magnesium (Mg) and Lanthanum (La) ions have been co-doped onto TiO 2 and used for the fabrication of photoanodes for DSSC. The doped TiO 2 particles were characterized by SEM, XRF, XRD, Raman, XPS and UV–vis diffuse reflection spectroscopy. The fabricated cells were characterized by I-V and EIS techniques. XRD and Raman measurements performed on the doped powders showed only peaks ascribed to pure anatase. The particle sizes were significantly reduced by doping with the double metal ions, La and Mg, as calculated by the Scherrer equation using the anatase XRD 101 peaks. Current - voltage measurements on the fabricated DSSC presented maximum photoelectric conversion efficiency (PCE) of 8.04% from cells with 0.5 mol.% Mg and La co-doped TiO 2 anodes (0.5MgLa-TiO 2 ), which gave a 20% improvement over cells with pure TiO 2 anodes that had 6.7% PCE. The DSSC performance reduced gradually to 6.67 and 5.45 as the concentration of the co-dopants, Mg and La increased to 1 and 2 mol.% respectively. DSSC with 1 mol.% Mg doped TiO 2 photoanodes (1Mg-TiO 2 ) and 1 mol.% La doped TiO 2 photoanodes (1La-TiO 2 ) reached 6.8% and 7.6% PCE, respectively, lower than that of 0.5MgLa-TiO 2 . EIS analysis showed that the DSSC with co-doped TiO 2 anodes indicated an overall stronger resistance to charge recombination with the electrolyte than those with the single doped and pure TiO 2 photoanodes. 0.5MgLa-TiO 2 was found to be the optimum concentration for DSSC efficiency with reduced charge recombination. This is attributed to the elevation of free surface state energy and the presence oxygen vacancy (trap states) as compared to pure TiO 2 .

An improvement in the efficiency of Ixora ( Ixora sp. (Rubiaceae)) floral dye sensitized solar cells (DSSCs) has been achieved by diminishing the pigment’s interactions. Liquid column chromatography (LCC) separated the dye components, namely aurone, pelargonidin, and derivatives of cyanidin & malvidin, showed improved photovoltaic performance when compared to cells sensitized by the original dye extract of Ixora. The LCC separated dye components were analyzed using UV–Vis, fluorescence and Fourier transform infrared (FTIR) spectroscopic studies. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and band gaps of the dyes were investigated. The DSSC prepared with the LCC separated dye showed energy conversion efficiencies (ECEs) ranging from 0.203% to 0.951%, whereas the original Ixora dye sensitized cell showed an ECE of 0.381%. Transient photovoltage (TPV) measurements and electrochemical impedance spectroscopy (EIS) were used to elucidate the photovoltaic parameters.

Chlorophyll and xanthophyll dyes extracted from a single source of filamentous freshwater green algae (Cladophora sp.) were used to sensitize dye sensitized solar cells and their performances were investigated. A more positive interaction is expected as the derived dyes come from a single natural source because they work mutually in nature. Cell sensitized with mixed chlorophyll and xanthophyll showed synergistic activity with improved cell performance of 1.5- to 2-fold higher than that sensitized with any individual dye. The effect of temperature and the stability of these dyes were also investigated. Xanthophyll dye was found to be more stable compared to chlorophyll that is attributed in the ability of xanthophyll to dissipate extra energy via reversible structural changes. Mixing the dyes resulted to an increase in effective electron life time and reduced the process of electron recombination during solar cell operation, hence exhibiting a synergistic effect.

Composites consisting of conducting polymers and nanosized semiconductor particles are scientifically and technologically attractive because of their unique electronic and optical properties. These properties were found to depend on the size of the embedded particles. In this study such nanocomposites with polyaniline (PANI) conducting polymers are reported. The results have shown that CdS and Cu2S nanocrystals can be successfully incorporated into a polyaniline matrix and their particle sizes can be controlled by adjusting the concentration of the additives. Photovoltaic devices with CdS/PANI systems of various CdS concentrations were fabricated and their performance were investigated. The short circuit current (ISC) and open circuit voltage (VOC) of these devices were found to increase with the concentration of CdS in the polymer matrix. The use of nanocrystals allows great flexibility in controlling the performance of the devices by changing the size, concentration and the material of the nanocrystals.

Possibility of use of dye extract from skin samples of a seasonal, indigenous fruit from Borneo, namely Canarium odontophyllum, in dye sensitized solar cells (DSSCs) are explored. Three main groups of flavonoid pigments are detected and these pigments exhibit different UV-vis absorption properties, and hence showing different light harvesting capabilities. When applied in DSSCs. The detected pigment constituents of the extract consist of aurone (maritimein), anthocyanidin (pelargonidin) and anthocyanidin (cyanidin derivatives). When tested in DSSC, the highest conversion efficiency of 1.43% is exhibited by cyanidin derivatives, and this is followed by conversion efficiencies of 0.51% and 0.79% for aurone and pelargonidin, respectively. It is shown that individual pigments, like cyanidin derivatives and pelargonidin, exhibit higher power conversion efficiency when compared to that of C.odontophyllum skin pigment mixture (with a conversion efficiency of only 0.68%). The results indicate a possibility of masking effects of the pigments when used as a mixture. The acidification of C.odontophyllum skin pigments with concentrated hydrochloric acid improves the conversion efficiency of the mixture from 0.68% to 0.99%. The discussion in this paper will draw data and observations from the variation in absorption and adsorption properties, the HOMO-LUMO levels, the energy band gaps and the functional group compositions of the detected flavonoids.

It has been found that the emeraldine base (EB) form of polyaniline can be protonated through functionalized protonic acid. Also EB can be fully oxidized to pernigraniline base (PNB) and this form is of interest because it is the only known polymer other than polyacetylene with two fold degenerate ground states. The present study is devoted to a qualitative investigation of PNB using absorption spectroscopy as a primary tool. From measurements of the optical absorption of pernigraniline and emeraldine at various acid concentrations, it can be concluded that the base forms become significantly protonated and the protonation depends not only on the protonating agent but also on the solvent.