N-Heterocyclic carbene-based tetradentate platinum() complexes for phosphorescent OLEDs with high brightness

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 1; no. 1; pp. 21 - 218
• Main Authors: Li, Guijie, Liu, Shun, Sun, Yulu, Lou, Weiwei, Yang, Yun-Fang, She, Yuanbin
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 23.12.2021
• Subjects: Brightness; Emitters; Organic light emitting diodes; Phosphorescence; Quantum efficiency; Room temperature
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d1tc05207a

Organic light-emitting diode (OLED) is an attractive technology for display applications in high-end electronics. Tetradentate Pt( ii ) complexes are phosphorescence emitters of great importance for OLED fabrication. A novel series of N-heterocyclic carbene (NHC), benzocarbene (Ph/NHC) and pyridinocarbene (Py/NHC)-based tetradentate Pt( ii ) complexes with fused 5/6/6 metallocycles was designed and developed. Their electrochemical and photophysical properties were systematically studied through experimental and theoretical investigations, which were greatly affected by the NHC, Ph/NHC and Py/NHC. Pt(NHC-1) shows a dominant emission peak at 509 nm with a quantum efficiency of 40% and an excited lifetime of 1.8 μs in a 5 wt% doped PMMA film at room temperature. A Pt(NHC-1)-doped green OLED using 26mCPy as the host material demonstrated a very high L max of 64 416 cd m −2 , which was a record-high value for the reported Pt( ii ) complex-based phosphorescent OLED. The OLED also achieved a peak EQE of 13.1% with small efficiency roll-off, which still maintained EQEs of 12.8%, 11.6% and 8.6% at a high brightness of 100, 1000 and 10 000 cd m −2 . A novel series of NHCs-based tetradentate Pt( II ) complexes were designed and developed. Pt(NHC-1)-based green OLED achieved a maximum luminescence of 64 416 cd m −2 , which was a record-high value for reported Pt( II ) complexes-based phosphorescent OLEDs.