Designing hierarchical structures of complex electronically conducting organic polymers via one-step electro-polymerization

Abstract

Thermal chemical synthesis of conjugated polymers has often been plagued by low product yields, by-product contamination and high-cost catalysts. Electrochemical synthesis is an alternative strategy that can overcome these failures to obtain highly efficient syntheses. Herein, we present the study of diketopyrrolopyrrole-bisthiophene (DPPT₂), diketopyrrolopyrrole-bisfuran (DPPF₂) and thienothiadiazole-bisthiophene (TTDT₂) for diblock copolymerization with terthiophene (T₃) as a π-linker to form tunable narrow band gap polymers. The polymers suspended as thin films have similar redox characteristics to the monomers with potential shifts that prove the identity of the respective polymers. Electrochemical impedance measurements were carried out in the −0.6 V to 1.0 V potential range with an average electron transport resistance (R_e) value of 110 Ω irrespective of the applied potential. This confirms the polymers to have higher intrinsic electrical conductivity. The atomic ratios of the synthesized materials were calculated experimentally using energy dispersive X-ray (EDX) analysis, and they confirm the theoretical composition of the polymers. These doped polymers exhibit absorption bands in the visible to SWIR region (800–1800 nm) with optical band gaps from 0.773 to 1.178 eV in both the solid and the solution state.