Ladder-type heteroacenes with well-defined structures and highly planar and delocalized p-electrons are an important class of materials for potential applications in organic electronics. The incorporation of heteroatoms into the ladder backbone allows for tuning optical-electronic properties and crystal structures in the solid state. Significant progress in synthesis and physical studies of a number of fascinating ladder molecules has been achieved. This review discusses progression in synthetic methods, structural characterization, and applications of ladder-type heteroacenes.
A critical issue in developing high-performance organic light-emitting transistors (OLETs) is to balance the trade-off between charge transport and light emission in a semiconducting material. Although traditional materials for organic...
We describe the synthesis as well as the optical and charge-transport properties of a series of donor-acceptor (D-A) ladder-type heteroacenes. These molecules are stable, soluble, and contain up to 24 fused rings. Structural analyses indicated that the backbones of S 10r and Se 10r are bent in single crystals. The three 10-ring heteroacenes were functionalized with thiol anchoring groups and used for single-molecular conductance measurements. The highest conductance was observed for molecular wires containing a benzoselenadiazole (BSD) moiety, which exhibits the narrowest band gap. Multiple charge-transport pathways were observed in molecular wires containing either benzothiadiazole (BTD) or BSD. The conductance is a complex function of both energy gap and orbital alignment.
The lack of design principle for
developing high-performance polymer
materials displaying strong fluorescence and high ambipolar charge
mobilities limited their performance in organic light-emitting transistors
(OLETs), electrically pumped organic laser, and other advanced electronic
devices. A series of semiladder polymers by copolymerization of weak
acceptors (TPTQ or TPTI) and weak donors (fluorene (F) or carbazole
(C)) have been developed for luminescent and charge transporting properties.
It was found that enhanced planarity, high crystallinity, and a delicate
balance in interchain aggregation obtained in the new copolymer, TPTQ-F,
contributed to high ambipolar charge mobilities and photoluminescent
quantum yield. TPTQ-F showed excellent performance in solution-processed
multilayered OLET devices with an external quantum efficiency (EQE)
of 5.3%.
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