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TiO 2 electrodes adsorbed with two natural dyes (gardenia yellow and monascus) were used as sensitizers to improve the conversion efficiency of cocktail dye-sensitized solar cells (CDSC) for light harvesting over a wide range of wavelength. Adsorption and electrochemical properties of two dyes were evaluated based on adsorption kinetics and electrochemical measurements. In addition, the photovoltaic performance of a photo-electrode adsorbed with single-dye (gardenia yellow and monascus) or the mixture or successive adsorption of the two dyes, was evaluated from current–voltage measurements. Layered co-sensitization of the two natural dyes was compared depending on the adsorption modes. As for the TiO 2 electrode with successive adsorption of monascus and gardenia yellow dyes, the solar cell yields a short-circuit current density ( J sc ) of 2.04 mA/cm 2 , a photovoltage ( V oc ) of 0.63 V, and a fill factor of 0.64, corresponding to an energy conversion efficiency ( η ) of 0.82%. [ABSTRACT FROM AUTHOR]

The adsorption characteristics of C.I. Reactive Orange 16 (RO 16) from aqueous solution onto residual brewery yeast were investigated under various experimental conditions. At pH 3.0 and 308 K, the adsorption capacity of RO 16 onto residual brewery yeast was found to be 0.56 mol/kg. Experimental data indicated that the adsorption capacity of residual brewery yeast for the dye was higher in acidic, than in neutral or basic solutions. The adsorption equilibrium data showed good correlation with the Langmuir isotherm models. The estimated values for the free energy of adsorption (Δ G o ) were −6.661, −4.812 and −3.929 kJ/mol at 288, 298 and 308 K, respectively, which indicated that a spontaneous process had occurred. The negative values of enthalpy (Δ H o ) and entropy (Δ S o ) indicated the exothermic nature of the adsorption of RO 16 onto residual brewery yeast. Kinetic studies showed that the biosorption of RO 16 onto residual brewery yeast in the system followed pseudo-second order kinetics. [ABSTRACT FROM AUTHOR]

Highlights: [•] Adsorption kinetics of Monascus red dye as sensitizer was investigated. [•] Electrochemical properties in Monascus DSSC were found to be solvent-dependent. [•] Photovoltaic efficiencies were dependent on the adsorption characteristics. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the amount of dye molecules adsorbed on TiO2 thin films in dye-sensitized solar cells (DSSCs), it is essential to conduct the adsorption of dyes and desorption with NaOH. However, these steps are complex, time-consuming and prone to inaccuracy. A novel adsorption apparatus was made in our laboratory to understand the adsorption mechanism of dye molecules on TiO2 thin film and also obtains the precise adsorption amount without a desorption step. The commercial and natural dyes, N719 and gardenia yellow, respectively, were employed to measure the adsorption kinetic data, which were analyzed by pseudo-first-order and pseudo-second-order models. It was found that the adsorption apparatus developed in this work for DSSCs was very effective and enabled the precise measurement of the amount of dye adsorbed on the TiO2 thin film directly without a desorption step. [Copyright &y& Elsevier]

Abstract: Dye-sensitized solar cells (DSSCs) were assembled using natural dyes extracted from Gardenia Jasminoide Ellis as sensitizers. Different mixtures of natural dyes (i.e., gardenia yellow (GY) and gardenia blue (GB)) extracted from the natural flower of Gardenia Jasminoide Ellis were used to produce photosensitivity by interaction between the chemisorption and physisorption of the dyes and the surface of porous TiO2 film. In this paper, the adsorption characteristics for harvesting sunlight and the electrochemical behavior of electron transfer using GY and GB, and also a mixture of both dyes were investigated. The light absorption spectrum of the mixed extract contained peaks corresponding to the contributions from both gardenia yellow and gardenia blue extracts. The energy conversion efficiency of the TiO2 electrode with successive adsorptions of GY and GB dye (S-GYB) was 0.59%, which is enhanced compared to the cases of single-dye adsorption. [Copyright &y& Elsevier]

To improve the photovoltaic conversion efficiency in dye-sensitized solar cells (DSSCs), TiO 2 electrode adsorbed with gardenia yellow purified by nonionic polymeric sorbent was successfully formulated on nanoporous TiO 2 surface. Adsorption and desorption properties of crude gardenia yellow solution on a macroporous resin, XAD-1600, were investigated to purify gardenia yellow because of its strong adsorption and desorption abilities as well as high selectivity. To this end, adsorption equilibrium and kinetic data were measured and fitted using adsorption isotherms and kinetic models. Adsorption and desorption breakthrough curves in a column packed with XAD-1600 resin was obtained to optimize the separation process of gardenia yellow. The photovoltaic performance of the photo-electrode adsorbed with the crude and purified gardenia yellow in DSSCs was compared from current–voltage measurements. The results showed that the photovoltaic conversion efficiency was highly dependent on how to separate and purify gardenia yellow as a photosensitizer. [ABSTRACT FROM AUTHOR]