Tuning Singlet and Triplet Excited State Energies and Frontier Orbitals of Imidazole Host/Emitter for Hybrid White OLEDs

Conference · Tue Jul 23 00:00:00 EDT 2019

DOI:https://doi.org/10.2172/1797702· OSTI ID:1797702

Idris, Muazzam ^[1]; Soh, Chan Ho ^[2]; Djurovich, Peter I. ^[3]; Forrest, Stephen R. ^[2]; Thompson, Mark E. ^[3]

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1. Univ. of Southern California, Los Angeles, CA (United States); University of Southern California, Los Angeles, CA
2. Univ. of Michigan, Ann Arbor, MI (United States)
3. Univ. of Southern California, Los Angeles, CA (United States)

In this work, we report hybrid fluorescent/phosphorescent WOLEDs employing blue fluorescent and green and red phosphorescent emitters doped into a host matrix. The fluorescent emitting dopant harnesses all electrically generated high energy singlet excitons for blue emission, and the phosphorescent dopants harvest the remainder of lower-energy triplet excitons for green and red emission. This design requires the singlet state (S1) of the host to be higher than the S1 of the fluorescent dopant so that the singlet excitons generated on the host are transferred to the fluorescent dopant. Furthermore, the triplet state (T1) of the host matrix should be lower than the T1 of the fluorescent dopant so the triplet excitons generated on the fluorescent dopant can be transferred to the host matrix which will then be transferred to the green and red phosphors. To develop a host material that can serve this purpose, we tune the electronic properties of phenanthro[9,10-d]imidazole by incorporating phenyl and/or pyridyl moieties at the N1 and C2 positions of phenanthro[9,10-d]imidazole. This substitution resulted in variety of host materials with different singlet/triplet energies, quantum efficiency and redox values. The resulting phenanthro[9,10-d]imidazoles are employed as host materials for fluorescent and phosphorescent dopants and as neat fluorescent emitters. Monochromatic devices with a fluorescent emitter and the phenanthro[9,10-d]imidazoles as host materials or as neat fluorescent emitter achieved near theoretical maximum efficiency. Finally, efficient three-color hybrid WOLEDs were fabricated using the phenanthro[9,10-d]imidazoles as hosts for a fluorescent dopant or as neat fluorescent emitters and host for green and red phosphors.

• Research Organization: University of Southern California, Los Angeles, CA
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: EE0008244
• OSTI ID: 1797702
• Report Number(s): Conference Poster: DOE-USC-08244-2
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
solid state lighting
OLED
organic LED