Deep Blue Phosphorescence from Platinum Complexes Featuring Cyclometalated -Pyridyl Carbazole Ligands with Monocarborane Clusters (CBH).

The utilization of deep blue phosphorescent materials in high-performance displays and solid-state lighting requires high quantum efficiencies and color purities. Here, we describe the preparation and luminescent properties of novel platinum triplet emitters featuring cyclometalated -pyridyl-carbazole ligands functionalized with -monocarborane clusters [CBH]. All reported complexes were fully characterized by using standard small molecule techniques (UV-vis, cyclic voltammetry, nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS)), and their solid-state structures were elucidated by X-ray diffraction. These platinum phosphors emit in the blue region of the visible wavelength spectrum in both the solid and solution states. Complex exhibits the highest luminous efficiency at λ = 439 nm with a photoluminescent quantum yield (PLQY) of 60% by dispersing in a PMMA matrix. Electrochemical and computational studies of complexes and revealed that the blue phosphorescence originates mainly from intraligand π → π* (ILCT) transitions with relatively small MLCT mixing. A deep-blue OLED containing as the light-emitting dopant was successfully fabricated using a solution-processed method, and the device exhibited blue photoluminescence with CIE coordinates of (0.17, 0.15) and a maximum external quantum efficiency (EQE) value of 6.2%. This article represents the pioneering study of a deep blue PhOLED using a Pt complex bearing a -monocarborane anion substituent, providing a new avenue into the preparation of novel triplet emitters based on boron-rich cluster anions.