Polymerization of tellurophene derivatives by microwave-assisted palladium-catalyzed ipso-arylative polymerization

We report the synthesis of a tellurophene-containing low-bandgap polymer, PDPPTe2T, by microwave-assisted palladium-catalyzed ipso-arylative polymerization of 2,5-bis[(α-hydroxy-α,α-diphenyl)methyl]tellurophene with a diketopyrrolopyrrole (DPP) monomer. Compared with the corresponding thiophene analog, PDPPTe2T absorbs light of longer wavelengths and has a smaller bandgap. Bulk heterojunction solar cells prepared from PDPPTe2T and PC₇₁BM show PCE values of up to 4.4 %. External quantum efficiency measurements show that PDPPTe2T produces photocurrent at wavelengths up to 1 μm. DFT calculations suggest that the atomic substitution from sulfur to tellurium increases electronic coupling to decrease the length of the carbon-carbon bonds between the tellurophene and thiophene rings, which results in the red-shift in absorption upon substitution of tellurium for sulfur. Telluric rings: The tellurophene-containing low-bandgap polymer PDPPTe2T, prepared by microwave-assisted ipso-arylative polymerization, exhibited red-shifted absorption spectra compared to the thiophene analogue. Bulk heterojunction solar-cell devices from PDPPTe2T and PC₇₁BM reach a power conversion efficiency of 4.4 % and produce photocurrent at wavelengths up to 1 μm.