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 <b>P-BPDTT</b> and <b>P-BPDBT</b> which entail <b>BPD</b>, a Pechmann dye framework, as electron accepting moieties, and thieno­[3,2-<i>b</i>]­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. <b>P-BPDTT</b> possesses lower LUMO level and narrower bandgap than <b>P-BPDBT</b>. On the basis of the characterization of the field-effect transistors, a thin film of <b>P-BPDTT</b> 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 <b>P-BPDBT</b> only shows <i>p</i>-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

Conjugated Random Donor–Acceptor Copolymers of [1]Benzothieno[3,2‑<i>b</i>]benzothiophene and Diketopyrrolopyrrole Units for High Performance Polymeric Semiconductor Applications

Three-component random copolymers having different ratios of [1]­benzothieno­[3,2-<i>b</i>]­benzothiophene (BTBT) and diketopyrrolopyrrole (DPP) units were synthesized, and their application in organic field effect transistors (OFET) has been discussed. These low band gap polymers exhibit p-type semiconducting properties, and it has been observed that increase in the percentage composition of the fused chalcogenophene (BTBT) in the polymer backbone significantly improves the charge carrier mobility (μ_h) up to 2.47 cm² V^–1 s^–1. The GIXRD technique and AFM have been used to explain the influence of BTBT on the nature of molecular packing in the polymer thin films. These results unveil the role of the effective conjugation length as well as the intermolecular ordering of the polymer chains on the charge carrier transport in OFET