π-conjugated polymer-fullerene covalent hybrids via ambient conditions Diels-Alder ligation

The established ability of graphitic carbon-nanomaterials to undergo ambient condition Diels-Alder reactions with cyclopentadienyl (Cp) groups is herein employed to prepare fullerene-polythiophene covalent hybrids with improved electron transfer and film forming characteristics. A novel precisely designed polythiophene (M _n 9.8 kD, D strok sign 1.4) with 17 mol% of Cp-groups bearing repeat unit is prepared via Grignard metathesis polymerization. The UV/Vis absorption and fluorescence (λ_ex 450 nm) characteristics of polythiophene with pendant Cp-groups (λ_max 447 nm, λ_e-max 576 nm) are comparable to the reference poly(3-hexylthiophene) (λ_max 450 nm, λ_e-max 576 nm). The novel polythiophene with pendant Cp-groups is capable of producing solvent-stable free-standing polythiophene films, and non-solvent assisted self-assemblies resulting in solvent-stable nanoporous-microstructures. ¹H-NMR spectroscopy reveals an efficient reaction of the pendant Cp-groups with C₆₀. The UV/Vis spectroscopic analyses of solution and thin films of the covalent and physical hybrids disclose closer donor-acceptor packing in the case of covalent hybrids. AFM images evidence that the covalent hybrids form smooth films with finer lamellar-organization. The effect is particularly remarkable in the case of poorly soluble C₆₀. A significant enhancement in photo-voltage is observed for all devices constituted of covalent hybrids, highlighting novel avenues to developing efficient electron donor-acceptor combinations for light harvesting systems. Fullerene-polythiophene covalent-hybrids are achieved by exploiting the natural ability of pristine carbon nanomaterials to undergo ambient condition Diels-Alder reactions with cyclopentadienyl (Cp) groups. A novel polythiophene with pendant Cp-groups prepared via GRIM polymerization is employed to fabricate these covalent-hybrids that exhibit a higher extent of fluorescence quenching and smoother films with fine lamellar texture compared to physical hybrids.