A novel design strategy for tetradentate Pt(ii) complexes using conformation managers to achieve high-efficiency, narrow-emission blue organic light-emitting diodes

Abstract

In this study, we developed a molecular design strategy for tetradentate Pt(II) complexes to improve the efficiency and color purity of blue phosphorescent organic light-emitting diodes (PhOLEDs). The strategy involves the introduction of a conformation manager at the 4-position of benzimidazolyl carbene in a tetradentate ligand. Methyl and phenyl groups were employed as conformation managers to enhance the rigidity of the molecule, thereby improving the radiative process and suppressing vibrational emission. The conformation managers inhibited π-conjugation extension to the N-substituent, blue-shifting the emission spectrum and stabilizing the lowest unoccupied molecular orbital level of the ligand. The Pt(II) complexes embedded with the conformation managers achieved small full-width at half maximum (FWHM) values, blue-shifted emission spectra, and high external quantum efficiencies (EQEs). The blue PhOLEDs with methyl- and phenyl-incorporated Pt(II) complexes exhibited small FWHMs of 18 and 20 nm, high EQEs of 27.1% and 27.5%, and CIE_y coordinates of 0.084 and 0.100, respectively, indicating that the devices outperform other reported Pt(II) complex based blue PhOLED devices. These results demonstrate that, by embedding a conformation manager in tetradentate ligands, blue PhOLED devices with narrowband emission, high EQEs, and improved color purity can be achieved.