Phenylene Thiophene Research Articles

Microdisk and Microring Lasers of Thiophene–Phenylene Co‐Oligomers Embedded in Si/SiO2 Substrates

Microdisk and microring lasers of the organic semiconductor material thiophene/phenylene co-oligomer (TPCO) have been fabricated on Si/SiO2 substrates. Laser emission with the whispering gallery modes (WGM) is observed in 0-1 vibration transitions. Comparing with the bulk film parts, a few times reduction of the lasing threshold has been observed in microdisks. Microring lasing threshold is reduced further when the width of the waveguide is less than 1 μm. WGM with waveguide confinement is supposed to contribute to the decrease of the threshold.

Investigation of Solubility−Field Effect Mobility Orthogonality in Substituted Phenylene−Thiophene Co-oligomers

We report here on our investigations of structure−property correlations in soluble organic semiconductors. To develop formulations for mass printing of semiconductor films, a series of alkoxy- and alkyl- disubstituted symmetric phenylene thiophene co-oligomers (disubstituted-PTTP) were systematically synthesized to achieve high solubility in common organic solvents. Solubilities of up to 40% by weight in tetrahydrofuran at room temperature were achieved by introducing branching at various positions on the terminal chains, and by silyloxy or hydroxy functionalization of the chains. Concomitant with the solubility increase, however, mobilities and Ion/Ioff ratios of these materials in TFT devices fall several orders of magnitude. X-ray diffraction of the semiconductor films reveals increasing tilt of the molecular orientation on the substrate with an increase in steric crowding near the PTTP core. This indicates that π-stacking of these molecules along the channel between the source and drain is hampered and leads to the observed inverse interdependence of solubility and the field effect mobility.

DFT calculations of the local spin densities and oligomerization mechanism of thiophene–phenylene (TP) co-oligomers and derivatives

In this work we are going to combine the DFT calculations with experimental results on three types of copolymers based on phenylene and thiophene. First and for obtaining a theoretical basis for the one-step formation of poly(2-phenylthiophene) (TP) and derivatives. The electronic states of three monomers based on thiophene and phenylene (TP) were elucidated by molecular orbital calculations using DFT (B3LYP/6-31G ∗). Then, the reactivity for coupling reaction of TP and derivatives are inferred from the unpaired electron spin densities of the respective radical cations. The major regio-selective product of the polymerization can be well understood in term of the magnitude spin densities. Our goal is initially to propose an oligomer model by examining the initiating and propagating reaction based on this theoretical study. Then, to investigate the effect of alkyl and alkoxy groups, attached on phenylene ring, on various properties of copolymer by examining structural and electronic properties.

Influence of the introduction of phenylene units into the polymer backbone on bandgap of conjugated poly(heteroarylene methines)

A series of conjugated poly(heteroarylene methines) containing alternating aromatic and quinoid phenylene–thiophene moieties in the main chain have been synthesized. These polymers are soluble in common organic solvents, such as chloroform, THF. The optical and electrochemical properties of the conjugated poly(heteroarylene methines), such as band gap, redox potentials, ionization potential, and electron affinity, were found to be significantly modified by the size of lateral groups on phenylene units and the number of phenylene units on the phenylene–thiophene moieties. With the increase of the size of lateral groups on phenylene units, the polymers show much bigger conjugated length. And the introduction of two phenylene units between two thiophene units lowers much more band gap than that of one phenylene unit.

Light emitting oligomers containing 2,3,4,5-tetraphenylthiophenyl moiety and silyl linkage

Light emitting oligomers of high photoluminescence (PL) quantum efficiency were prepared and emphasized in this study. Thereby, four light emitting oligomers containing 2,3,4,5-tetraphenylthiophene (TP) moiety were prepared by Heck coupling between 2,5-bis(4-bromophenyl)-3,4-diphenylthiophene and four diene monomers. Certain diene monomers containing silyl unit were especially used in an attempt to introduce π–σ conjugation into the oligomeric products. Four products exhibited similar UV-Vis absorption and emission properties, with their absorption maxima ( λ max) ranged from 338 to 391 nm and emission maxima (PL max) from 487 to 505 nm. Quantum efficiency for the photoluminescent process was enhanced due to the inherently alternative phenylene–thiophene ring structure in the TP moiety and the silyl units introduced. Quantum efficiency was particularly increased from 28% to a value of 61–74%, if products were prepared from silyl-containing dienes instead of simple aliphatic diene monomer. With the incorporation of bulky TP moiety, four products were basically amorphous in nature and exhibited thermal stability at elevated temperatures.