Rational Molecular Design Strategy for Host Materials in Thermally Activated Delayed Fluorescence-OLEDs Suitable for Solution Processing

• Published in: ACS applied materials & interfaces Vol. 15; no. 23; pp. 28277 - 28287
• Main Authors: Kwon, Na Yeon, Park, Su Hong, Koh, Chang Woo, Park, Jin Young, Kang, Min Ji, Baek, Heume Il, Youn, Junho, Park, Sungnam, Han, Chang Wook, Cho, Min Ju, Choi, Dong Hoon
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.06.2023
• Subjects: Organic Electronic Devices; non-conjugated linker; thermally activated delayed fluorescence; solution-process; organic light-emitting diode; V-shaped host
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.3c01236

Herein, a novel core molecule for V-shaped host molecules was synthesized, wherein two carbazoles were directly linked to cyclohexane. Cy-mCP and Cy-mCBP hosts were also successfully prepared for solution-processable thermally activated delayed fluorescence organic light-emitting diodes (TADF–OLEDs). The Cy-mCP and Cy-mCBP molecules contained a cyclohexane linker directly linked to two small molecular hosts (mCP and mCBP), exhibiting twice the molecular weight while maintaining the basic properties of a single host molecule with improved film-forming ability and solubility in organic solvents. These host materials showed superior thermal stability and high glass transition temperatures compared to lower molecular weight hosts. Green TADF–OLEDs were prepared using the two host materials and 2,4,5,6-tetra­(3,6-di-tert-butylcarbazol-9-yl)-1,3-dicyanobenzene (t4CzIPN) emitter, achieving device efficiencies similar to that of a low-molecular-weight host. However, after the incorporation of a V-shaped host, superior characteristics were observed in terms of the thermal stability and operational stability of the device. The synthesis of V-shaped molecules by directly linking two carbazoles to a cyclohexane linker is promising for the development of different hosts for solution-processable OLEDs.