Branched Oligophenylenes with Phenylene–Ethynylene Fragments as Anode Interfacial Layer for Solution Processed Optoelectronics

Abstract

Two branched oligophenylenethynylenes with phenylene or biphenylene moieties as inter‐nodal fragments are synthesized by the Sonogashira reaction for optoelectronic applications. The branching of polyphenylenethynylenes influences the electro‐optical properties, but cannot be precisely controlled, while its determination is often hardly addressed. The optical investigation, supported by nuclear magnetic resonance (NMR) studies, of oligophenylenethynylenes and the properly synthesized model compounds is performed to get insights on the branching and related effect on the material performance. The proposed branched oligophenylenethynylenes are good ultraviolet emitters in solution, while in solid‐state aggregation phenomena strongly affect emission properties. However, the interactions between π‐electrons on phenylene and ethynylene of neighboring molecules in films enhance intermolecular charge transport (hole mobility = 3.2 × 10−3 cm2 V−1s−1) making them optimal candidates as hole transport materials in optoelectronic devices. The insertion of the oligophenylenethynylene film as a hole transporting layer in multilayered solution processes blue, green, and red electroluminescent diodes, enhances OLEDs electro‐optical properties.

Polyphenylenepyridines Based on Acetylaromatic Compounds

“…For the absorption band at 803 cm −1 , the tendency to shift towards lower frequencies is preserved due to the conjugation effect when the substituent chain is extended [38]. A similar trend is observed in the IR spectra of polymers based on monomer 8b.The synthesized polymers contained residual terminal acetyl groups (absorption bands at 1680 cm −1 and 1270 cm -1 ) and fragments of dimerization condensation of acetyl groups (absorption band at 1655 cm -1 ).…”

“…The elemental analysis data confirm the trend that, with an increase in the percentage of TEOF in the reaction mixture, the amount of nitrogen in the polymer increases, and, consequently, of pyridine fragments too. Thus, when the percentage of TEOF was 3.6% For the absorption band at 803 cm −1 , the tendency to shift towards lower frequencies is preserved due to the conjugation effect when the substituent chain is extended [38]. A similar trend is observed in the IR spectra of polymers based on monomer 8b.…”

Thermally Activated Delayed Fluorescent (TADF) Mono‐Polymeric OLED with Higher EQE over Its TADF Repeating Unit

“…[25][26][27][28] In this context, polymeric materials came on the stage by virtue of great film-forming ability and good thermal stability, which are quite suitable for solution-processed OLED. [29][30][31][32][33][34][35] However, the methodology of the TADF polymers is less developed, with most of the introduction of TADF units into the TADF polymers. Because intense TADF units tend to result in severly triplet-triplet annnihilation to reduce the efficiency, most TADF polymers need complicated structure to separate the TADF units, making the preparation more time consuming and laborious.…”