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.