The First Example of Bisindole-Based Polyurethane Dendrimers: Synthesis and Performance in DSSC

A new B₃-type blocked isocyanate core and AB₂-type building block molecules containing bis-indole moiety were synthesized via a scalable synthetic routes. Starting with these molecules, amine- and blocked isocyanate-terminated polyurethane dendrimers up to third generation were build-up using (i) a simple urethane interchange reaction, (ii) deprotection of amine and (iii) efficient conversion of amine into blocked isocyanate groups. The structural integrity of the core, building block and their intermediates were verified using FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy and HR-MS technique. The structure and molecular weight of blocked isocyanate-terminated dendrimers were confirmed using ¹H-NMR spectra and size exclusion chromatography with multi angle laser light scattering detector (SEC-MALLS) technique respectively whereas the structure of all other dendrimers were confirmed using FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. Dye-sensitized solar cells (DSSC) were fabricated using these dendrimers as electrolytes; the DSSC fabricated with G3 dendrimer yielded an overall energy conversion efficiency (η) of 6.32 % upon illumination with 1 sun visible light.