Electronic Excited States of Carotenoid Dyes Adsorbed on TiO₂

Abstract

The fast development of new organic sensitizers for the purposes of dye-sensitized solar cells and photocatalysis requires a better understanding of the complexity of their electronic states on TiO2 surface. This paper describes a study of carboxylated derivatives of all-trans carotenoids retinoic acid (ATRA) and bixin by Stark effect (electroabsorption) spectroscopy in glassy ethanol at low temperature, both as free monomeric species and when adsorbed to nanoparticles of titanium dioxide in the presence of a variable concentration of acetic acid. Both pigments adsorbed strongly at the lowest acid contents (<0.2%), but become partially desorbed at the higher acid concentration (2%). Adsorption of pigments on TiO2 was accompanied by an increase of difference dipole moment Δμ between the ground and excited states from 14.5 to 22.5 D for ATRA. A smaller change in Δμ was estimated for bixin. The remarkable spectral inhomogeneity exhibited by significant fractions of both pigments with larger values of Δμ is ascribed to the differences in bonding to TiO2. The gradual spectral shift due to the charging of nanoparticles induced by the increasing acetic acid concentration was used to estimate the change in surface electric field of charged nanoparticles.

Investigation of Vegetable Tannins and Their Iron Complex Dyes for Dye Sensitized Solar Cell Applications

“…As seen in Fig. 2 The possible chemical reactions for the formation of ZnO nanoplate can be described as follows [8,9]; Zn(OH) are unstable intermediates and they are decomposed by microwave vibration by forming ZnO nuclei both (reaction 6) and (reaction8) [8,9]. We previously observed that the morphology of ZnO was changed by different KOH concentration.…”

“…The sensitizers are the photo-harvesting materials such as ruthenium complexes, organic synthetic and natural dyes [2][3][4][5]. Several natural dyes have been employed as sensitizers in DSSCs, such as anthocyanin [6][7][8], carotene [9][10][11], chlorophyll [12,13] and tannin [14]. The plant-derived natural dyes are low cost and highly available alternatives.…”

The analysis of morfology of electrodes used in dyesensitized solar cells

“…Nanocząstki we wszystkich trzech przypadkach miały postać białego proszku, który wymagał mechanicznego rozdrobnienia i utarcia w moździerzu. Do nanocząstek dodawany był spotykany w opisach literaturowych α-terpineol [3] oraz kwas octowy, wybrany ze względu na wykazany we wcześniejszych badaniach udział w zapobieganiu agregacji nanocząstek oraz korzystny wpływ na przekaz ładunku elektrycznego w ogniwach DSSC [2]. Powstała po rozdrobnieniu masa była nakładana na szkło, a następ-nie wygrzewana w temperaturze 450 o C przez 45 min.…”

Effect of ZnO Nanomaterial and Red and Green Cabbage Dyes on the Performance of Dye-Sensitised Solar Cells

“…Several natural dyes have been employed as sensitisers in DSSCs, such as anthocyanin [16], chlorophyll [18], and carotene [19]. Pratiwi et al [20] used dragon fruit and red cabbage anthocyanin dyes as sensitisers for DSSCs, with conversion efficiencies of 0.024% and 0.054%, respectively.…”