Fifth Generation Polyurethane Dendrimers Decorated with Protected Amine, Free Amine and Blocked Isocyanate End Groups: Synthesis and Electrolytic Performance to Increase the Efficiency of Dye-Sensitized Solar Cell

Fifth generation polyurethane dendrimers decorated with trifluoroacetamide, free amine and blocked isocyanate end-groups were prepared and their structures were confirmed using FT-IR, ¹H and ¹⁹F-NMR, MALDI-TOF MS and size exclusion chromatography (SEC-MALS) techniques. The hydrodynamic diameter and zeta potential of dendrimers were measured using dynamic light scattering (DLS) technique; the later parameter indicated that the dendrimer containing trifluoroacetamide end-group (1) stabilized more in the medium. The effect of different end-groups on photophysical, electrochemical and thermal properties of dendrimers were also evaluated; dendrimer with blocked isocyanate end-groups (3) absorbed low light, showed two redox potential and exhibited glass transition temperature (T_g). All the dendrimers were used as electrolytes in combination with LiI for N719 dye-sensitized solar cells (DSSCs) and found that the DSSC fabricated with blocked isocyanate-terminated dendrimer (3) yielded nearly 2.5 times high power conversion efficiency (ɳ=8.04% upon illumination with 0.5 sun intensity) compared to the cell fabricated with only LiI electrolyte.