N-Heterocyclic carbene-based tetradentate platinum(<scp>ii</scp>) complexes for phosphorescent OLEDs with high brightness

Organic light-emitting device (OLED) is an attractive technology for display application in high-end electronics. Tetradentate Pt(II) complexes are phosphorescent emitters of great importance for OLED fabrications. 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 greatly affected by the NHC, Ph/NHC and Py/NHC. Pt(NHC-1) shows dominant emission peak at 509 nm with a quantum efficiency of 40% and excited lifetime of 1.8 &#181;s in 5 wt% doped PMMA film at room temperature. Pt(NHC-1)-doped green OLED using 26mCPy as host material demonstrated a very high Lmax of 64416 cd/m2, which was a record-high value for the reported Pt(II) complexes-based phosphorescent OLEDs. The OLED also achieved a peak EQE of 13.1% with small efficiency roll-off, which yet maintained EQEs of 12.8%, 11.6% and 8.6% at a high brightness of 100, 1000 and 10000 cd/m2.