Organic light-emitting diodes with a PIN structure of only thiophene/phenylene co-oligomer derivatives

Abstract

Organic light-emitting diodes with trilayer PIN structures are fabricated using only thiophene/penylene co-oligomer derivatives: 5,5′-bis(4-biphenylyl)-2,2′-bithiophene (BP2T), 5″′-bis(4-trifluoromethylphenyl)[2,2′;5′,2″;5″,2″′]quaterthiophene (P4T-CF3), and 5,5′-bis-(4′-cyanobiphenyl-4-yl)-2,2′-bithiophene (BP2T-CN) as the P, I, and N materials, respectively. As designed from their expected frontier orbital energies, electroluminescence (EL) is obtained from the P4T-CF3 layer. When the BP2T layer is first deposited on an indium-tin-oxide (ITO) substrate, the device (Al:Li/BP2T-CN/P4T-CF3/BP2T/ITO) shows homogeneous EL. On the other hand, the device with an opposite deposition order (Au/BP2T/P4T-CF3/BP2T-CN/ITO) shows dotted EL with higher efficiency at lower bias voltages. By decreasing the deposition rate of the P4T-CF3 layer in the latter device, its morphological change results in homogeneous EL with increased density of dotted emission.

Polymorph- and molecular alignment-dependent lasing behaviors of a cyano-substituted thiophene/phenylene co-oligomer

“…2(e)) result in a partially allowed transition at the lowest excited energy level. 31,32,36,45 As the intermolecular distance between the two neighboring molecules shortens, the width of energy splitting increases, and the lowest excited energy level becomes more stable. Therefore, it is inferred that the emission color changed from green to yellow because the distance between the two closest neighboring molecules was shorter and the lowest excited energy level was more stabilized in the yellow polymorphs prepared by the liquid-phase growth method.…”

“…Meanwhile, the occurrence of aggregation-induced emission and aggregation quenching (concentration quenching) has been reported in many organic crystals and aggregates. 14 Among various organic crystals, single crystals of thiophene/ phenylene co-oligomers (TPCOs) 21,[34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] exhibit high PLQYs ranging from 40 to 63% even in the solid state. To develop high-performance organic lasers and organic light-emitting devices, materials that exhibit high PLQYs, irrespective of conformational and molecular packing changes, are required.…”

Impact of Furan Substitution on the Optoelectronic Properties of Biphenylyl/Thiophene Derivatives for Light-Emitting Transistors

“…Thiophene/phenylene derivatives have good mobility and high photoluminescence yield. In particular, due to its synthetic flexibility and strong polarizability, thiophene has received much attention for the development of optoelectronic devices for over a decade. , The presence of sulfur atoms in thiophene’s core gives rise to a strong intermolecular interaction and yields excellent charge carrier mobility. A a result, a large number of reports are available on these derivatives for a multitude of applications ranging from OFETS to OPVs. − …”