Imidazole-Pyrene Hybrid Luminescent Materials for Organic Light-Emitting Diodes: Synthesis, Characterization & Electroluminescent Properties

A series of multichromophoric, pyrene-imidazole-phenyl based hybrid luminescent small molecules ( PA, PI, PnB, PtB, PoM and PnDM) with different donating groups at the para position of the phenyl attached to N1 position of imidazole moiety were designed, synthesized, and characterized, for use in blue organic light-emitting diodes (OLEDs). The photophysical, thermal and electrochemical properties of the molecules were systematically investigated. All the molecules displayed delayed fluorescence at room temperature with a lifetime ranging from 7.1 to 8.5 mu s. The synthesized fragment molecules (tetraphenylimidazoles: IA, IoM and InDM) revealed high triplet energies of -2.90eV. Glass transition temperatures determined to range from 77 degrees C to 123 degrees C and decomposition temperatures are found to be above 280 degrees C. The molecules possess appropriate HOMO and LUMO energy levels for effective charge injection. The crystal structure for PI is reported. OLED devices were fabricated based on the pyrene-imidazole-phenyl hybrids as emitters and as dopants with CBP as host. OLED devices with PI doped (5% wt.) with CBP exhibits excellent device performance with a current efficiency of 9.82 cd/A, the power efficiency of 8.32 lm/W and external quantum efficiency of 4.64%. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

A series of multichromophoric small molecules based on pyrene-imidazole-phenyl hybrids were designed for blue OLED applications. These molecules exhibited delayed fluorescence, high triplet energies, appropriate HOMO/LUMO energy levels, and stable thermal performance. OLED devices doped with PI showed excellent device performance with high efficiency.