Synthesis And Photoelectric Properties Of Imidazole - Based Dye Sensitizer

The solar cells is a solar energy device by photoelectric conversion mode. The third generation solar cells (Dye-Sensitized Solar Cells, DSSC) have been extensively studied in the last two decades, for its low cost, non-polluting and high photoelectric conversion efficiency. Dye-sensitizer is the light response unit of DSSC, and plays the role of absorbing solar energy to generate photoelectrons. Non-metallic organic dye-sensitizers get widely studied for molecules designable, structures adjustable, raw materials varied and strong light absorption capability, long photo-generated electrons’lifetime. The basic structure of non-metallic organic dye-sensitizers is called D-π-A (Doner-π conjugation-Acceptor), and get some other structures after20years’research, such as D-D-π-A, D-π-π-A. However, non-metallic dye-ensitizers generally have some short comings, such as narrow range of visible light absorption, poor redox stability, poor thermal stability and lack of long-term work ability. Benzimidazole, triphenylimidazole were designed as the electron donor units in the experiment to increase the stability of the molecule, which were not been reported in the literature.Experimental synthesized9dye-sensitizers, benzimidazolyl electron donor based dye-sensitizers:p-(2-benzimidazolyl)-benzoic acid (PBIF), p-(2-benzimidazolyl)-cinnamic acid (PBIA), p-(2-benzimidazolyl)-π-cyano-cinnamic acid acid (PBIC), p-(2-(1-carboxy benzoyl benzimidazoleyl)-benzoic acid (TB-IF), p-(2-(1-p-benzoyl benzimidazole acrylic acid)-phenyl acrylic acid (TB-IA), p-(2-(1-p-(a-cyanoacrylate)-benzoyl benzimidazole)-a-cyano-cinnamic acid (TB-IC); and triphenyl imidazolyl electron donor based dye-sensitizers:1-H-3-(4-(4,5-diphenyl-lH-imidazolyl)-benzoic acid (TPIF),1-H-3-(4-(4,5-diphenyl-imidazolyl)-phenyl-acrylic acid (TPIA),1-H-3-(4-(4,5-diphenyl-imidazolyl)-phenyl-2-cyanoacrylate (TPIC). The molecular structures were characterized through IR, NMR, MS. Synthetic products were used as dye-sensitizers in preparing DSSC and the performance were detected and the results showed synthetic benzimidazolyl electron donor dye-sensitizers and triphenylimidazolyl electron donor dye-sensitizers each having a photosensitive property. The DSSC with TPIF, TPIA, TPIC as dye-sensitizer respectively, get a photoelectric conversion performance of1.47%,1.85%,1.98%, respectively. What’s more, the prepared DSSC generally had higher fill factor and the highest reached76%, indicated a longer lifetime of photo-generated electrons and higher photoeleetron injection efficiency of synthetic dye-sensitizers. UV-visible spectroscopy analysis showed PBIF, PBIA, PBIC characteristic absorption wavelength was about405nm, TB-IF, TB-IA, TB-IC characteristic absorption wavelength was about390nm, TPIP, TPIA, TPIC characteristic absorption wavelength was about410nm, and all of them have sharp absorption peaks, indicated strong absorption ability in characteristic absorption wavelength. The lower conversion efficiency of DSSC based on synthesized products were for the narrow range of absorption and negative absorption region.The visible absorption spectrum of TiO2semiconductor film sensitized by TPIA and TPIC, respectively, and the results showed that the dye-sensitizers had good sensitizing properties and the visible absorptionswere redshifts and the absorption range were widened. It was found that a higher concentration of the dye-sensitizer solution to improve battery performance to help, but it’s not a linear growth relationship. What’s more, the too long sensitized time was no help to improve the fill factor. A higher concentration of solution and longer time of sensitized time could increase the amount of dye-sensitizer adsorbed on TiO2semiconductor film, so the short circuit current density was increased. But the excessive dye-sensitizer may associate to aggregation effect and the photoelectron recombination was increased. What’s more, the short circuit current density (Jsc) was not increases linearly with the amount of adsorption was for higher extinction coefficient of dye-sensitizer. The synthesized imidazole-based dye-sensitizers’bandgap were narrower and conjugate performance were better than triphenyl amine dye-sensitizers with similar structure, which were more conducive to get photo-generated electron and charge separation. So the further studies on the imidazole-based dye-sensitizers were meaningful.