Influence of selenophene substitution in BDT-based copolymers on molecular packing and charge transport

Abstract

We report the design and synthesis of two new donor-acceptor copolymers, PBDTT-TPD and PBDTSe-TPD, incorporating N-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD) as the electron-acceptor unit benzo[1,2-b:4,5-b ']dithiophene (BDT) derivatives incorporating thiophene and selenophene as the electron-donor unit, respectively. To investigate the impact of substituting sulfur with selenium in the BDT core, we performed comprehensive structural, optical, and electrical characterizations. Compared to PBDTT-TPD, the selenophene-containing PBDTSe-TPD polymer exhibits a narrower optical bandgap, broader and red-shifted absorption spectra, and enhanced intermolecular interactions. As a result, the organic field-effect transistors (OFETs) fabricated with these polymers show hole mobilities of 0.0058 cm2/V<middle dot>s or PBDTT-TPD and 0.021 cm2/V<middle dot>s for PBDTSe-TPD. These results demonstrate that the strong quinoidal character and lower aromaticity of selenophene contribute to improved molecular packing and charge transport properties, highlighting its potential for high-performance organic electronic materials.Graphical AbstractWe investigate how selenophene substitution in BDT-based donor-acceptor copolymers modulates molecular packing and charge transport. Two polymers, PBDTT-TPD and its selenium analogue PBDTSe-TPD, were synthesized and comprehensively characterized. Selenophene incorporation narrows the electrochemical bandgap, red-shifts absorption, and strengthens pi-pi interactions, while slightly reducing long-range lamellar order