Synthesis Of Non-Conjugated Polymer Dye And Study On Its Application For Dye Sensitized Solar Cells

Dye sensitized solar cells (DSSCs) promise to be novel solar cells due to their using relatively low cost materials, possibility of large scale production and high power conversion efficiency. Dye sensitizers considered the crucial component serve as the solar energy absorber in DSSCs. The proprieties of sensitizers have a great influence on the light harvesting efficiency and the overall photoelectric conversion efficiency. Small molecular organic dyes have been widely investigated as photoactive layers for DSSCs. However, the small molecular organic dyes feature poor thermal stability which lead to shorten the device lifetime. Compared with small molecular dyes, the polymer dyes show a better thermal stability. Recently, conjugated polymer dyes have been used as sensitizers for DSSCs. To the best of our knowledge, non-conjugated polymer sensitizer has not been reported so far.In this presented article, we for the first time detail the design and synthesis of a non-conjugated polymer sensitizer PPF, which containing a classical Donor(diphenylamine)-Fluorene-Acceptor(cyanoacetic acid) architecture PF and a non-conjugated linkers backbone through the1,2-dibromobenzene via palladium-catalyzed polymerization with monomethylaniline moieties pendent groups onto the C9position fluorene unit.Thermal properties, electrochemical properties and optical properties of the dyes PF and PPF were investigated, and their performances as sensitizer in DSSCs were measured. PPF exhibited a good thermal stability with a5%weight-loss temperature (Td5%) of395℃. The available electrochemical data confirm that there is a reasonable driving force for both electron injection and oxidized regeneration in a DSSC format for dye PF and PPF. It was found that the DSSCs based on dye PF achieved a solar-to-electrical energy conversion efficiency of2.31%(J5C=5.81mA·cm-2, Voc=0.63V, ff=63%)under100X10-3W/cm2(AM1.5G), and PPF obtained0.29%(Jsc=0.96mA·cm-2, Voc=0.57V, ff=55%). While an additional0.1mM CDCA(chenodeoxycholic acid) was added to the PPF dye solution, the efficiency was improved to0.53%. Using the density functional theory (DFT) calculations to optimize molecular structure of PF and the TEM image of PPF, it was also found that the ellipsoid stereochemical structure of PPF results to dye aggregation and poor electron injection efficiency, which is main reason for poor solar cell performance.