Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (02): 255-262.doi: 10.3866/PKU.WHXB201211221

• THEORETICAL AND COMPUTATIONAL CHEMISTRY • Previous Articles     Next Articles

Extension of Conjugate π Bridge in Dye Molecules for Dye-Sensitized Solar Cells

ZHAN Wei-Shen, LI Rui, PAN Shi, GUO Ying-Nan, ZHANG Yi   

  1. Institute of Near-Field Optics and Nanotechnology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, Liaoning Province, P. R. China
  • Received:2012-08-07 Revised:2012-11-22 Published:2013-01-14
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (10974025, 61137005).

Abstract:

Taking dye D5 molecules as the prototype, different types and different elemental quantities of conjugate π bridge was used to design D-π-A organic molecules. Density functional theory (DFT) and timedependent density functional theory (TDDFT) were adopted to simulate the geometric structures, molecular orbital energy levels, and UV-Vis absorption spectra of the molecules, with the aim of finding conjugate π bridge in the sensitizer molecules for dye-sensitized solar cells (DSSCs). The absorption spectra of the molecules using “methenyl chains”,“furan rings” or “thiophene rings”,“methenyl chains and furan rings”, or “methenyl chains and thiophene rings” as conjugate π bridge showed a gradually increasing red-shifting trend. With increases in the number of conjugate π bridge elements, the absorption spectrum showed an intense red-shift, which weakened gradually; under the same conditions, the lowest unoccupied molecular orbital (LUMO) energy level of the molecules gradually decreased, and the highest occupied molecular orbital (HOMO) energy level gradually increased. The HOMO energy levels of the molecules with three“methenyl chain and furan ring”or“methenyl chain and thiophene ring”elements as conjugate π bridge were higher than the energy level of the redox electrolyte; in polar solutions, the HOMO energy levels of the molecules adopting two “methenyl chain and furan ring” or “methenyl chain and thiophene ring” elements as conjugate π bridge were higher than the energy level of the redox electrolyte. The absorption spectra of the organic sensitizer molecules with several “methenyl chain and furan ring” or “methenyl chain and thiophene ring” elements as conjugate π bridge showed an intense red-shift. These results showed that for DSSCs sensitizer molecules, it is not necessary to have many conjugate π bridge elements; one to two elements is typically enough.

Key words: Dye-sensitized solar cell, Organic photosensitizer, Conjugated bridge, Density functional theory, Methenyl chain, Furan ring, Thiophene ring

MSC2000: 

  • O641