New Donor–Acceptor–DonorMolecules withPechmann Dye as the Core Moiety for Solution-Processed Good-PerformanceOrganic Field-Effect Transistors.

In this paper, we report the synthesis and characterizationoftwo new D-A-D molecules (E)-5,5′-bis(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)-1,1′-bis(2-ethyl-hexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BTBPD) and (E)-5,5′-bis- (5-(benzo[b]furan-2-yl)thiophen-2-yl)-1,1′-bis(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BFBPD). They entail bipyrrolylidene-2,2′(1H,1′H)-dione (BPD, known as Pechmann dye) as theelectron-accepting core that is flanked by two benzo[b]thiophene moieties and two benzo[b]furan moieties,respectively. Crystal structures of BTBPDand BFBPDprovide solid evidence for the intermolecular donor–acceptor(D-A) interactions, which are favorable for improving charge transportperformance. Organic field-effect transistors (OFETs) were preparedbased on thin films of BTBPDand BFBPDthroughsolution-processed technique. OFETs of BTBPDexhibitrelatively high hole mobility up to 1.4 cm2V–1s–1with high on/off ratio up to 106. In comparison, the hole mobility of OFETs with BFBPD(0.14 cm2V–1s–1) is relatively low, because of the poor thin-film morphology andlow molecular ordering, even after annealing. Thin-film morphologicaland XRD studies were carried out to understand the variation of holemobilities after annealing at different temperatures. The presentstudies clearly demonstrate the potentials of BPDthatis planar and polar as the electron-acceptor moiety to build D-A moleculesfor organic semiconductors with good performance. [ABSTRACT FROM AUTHOR]