Alternating Conjugated Electron Donor–Acceptor Polymers Entailing Pechmann Dye Framework as the Electron Acceptor Moieties for High Performance Organic Semiconductors with Tunable Characteristics

In this paper, we report the design, synthesis and semiconducting behavior of two conjugated D–A polymers P-BPDTT and P-BPDBT which entail BPD, a Pechmann dye framework, as electron accepting moieties, and thieno­[3,2-b]­thiophene and 2,2′-bithiophene as electron donating moieties. Their HOMO/LUMO energies and bandgaps were estimated based on the respective cyclic voltammgrams and absorption spectra of thin films. P-BPDTT possesses lower LUMO level and narrower bandgap than P-BPDBT. On the basis of the characterization of the field-effect transistors, a thin film of P-BPDTT exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 1.24 cm² V^–1 s^–1 and 0.82 cm² V^–1 s^–1, respectively, after thermal annealing. In comparison, thin film of P-BPDBT only shows p-type semiconducting behavior with hole mobility up to 1.37 cm² V^–1 s^–1. AFM and XRD studies were presented to understand the interchain arrangements on the substrates and the variation of carrier mobilities.