After M. Grätzel described ruthenium complex dye-sensitized solar cells (DSSC), scientists’ interest in these new technologies has grown significantly. The synthesis of metal-free organic compounds is simpler, compared to the organic metal complexes, and the devices themselves are characterized by simplicity of construction and inexpensive raw materials. The achieved DSSC efficiency of 12.5% using the carbazole dye ADEKA-1 proved that metal-free organic dyes can compete with expensive metal complexes. To improve the performance of DSSC, it is necessary to optimize the structure of organic dyes. It is known from the literature that increasing the number of anchoring groups and/or pi-conjugation improves the extinction coefficient of the dye, i.e. increases the efficiency of the material.
The aim of this project is synthesis of the organic dyes containing Trioger‘s base central core and color determining chromophore sidechains and investigation of their photophysical properties in order to apply them in construction of the hybrid solar cells. The main goals were set as follows: i) investigate functionalization possibilities of the Trioger‘s base synthons and develop economical synthesis routes; ii) synthesize and investigate organic dyes containing Trioger‘s base central fragment and carboxyl group-containg chromophores that would enable binding of the molecules to the TiO2 electrode; iii) synthesize nonlinear organic dyes containing Trioger‘s base central core and sidechains bearing two different color determining chromophores which would allow for broader absorption of electromagnetic radiation; iv) investigate photophysical properties of the synthesized organic dyes and ability to efficiently convert solar energy to electrical.
Project funding:
Projects funded by the Research Council of Lithuania (RCL), Projects carried out by researchers’ teams
Project results:
We have demonstrated that Trioger’s base is an excellent precursor for the construction of nonlinear structure dyes with two anchoring groups which are able to bind to the surface of the TiO2 electrode. A series of such dyes, containing polymethine fragments of different lengths have been synthesized. Investigated compounds have a broad absorption in a visible light range (400-700 nm), both in solution and on TiO2 surface, which is very favorable for the construction of efficient hybrid solar cells. Increase in Stokes shift while lengthening the ? -conjugated bridge between triphenylamine and rhodanine is observed in the synthesized dyes. Additionally, energy levels (HOMO, LUMO) of the new dyes are also suitable for their application in the hybrid solar cells. Length of the polymethine chains, connecting the donor and acceptor fragments, have significant influence on the performance of the dyes in the hybrid solar cells. It is interesting to note that Trioger’s base derivatives show promise not only in the area of charge generation, but also in charge transport. During the investigation a number of derivatives containing Trioger’s base synthon were also tested as hole transporting materials.
Project results have been published in three publications in Chemistry an Asian Journal (IF=4.592), Dyes and Pigments (3,473) and Journal of Physical Chemistry C (IF=4,536). All these journals are in the first quartile (Q1) in thier respective JCR categories. Publication „A structural study of Troger’s base scaffold-based dyes for DSSC applications“ published in Dyes and Pigments has been named a key scientific article contributing to excellence in science and engineering research by Canadian organization „Advances In Engineering (AIE)“ (March 8, 2018, https://advanceseng.com/chemical-engineering/structural-study-trogers-base-scaffold-based-dyes-dssc-applications/).
Period of project implementation: 2015-07-01 - 2018-03-31
Project coordinator: Kaunas University of Technology
