Deep-blue emitters (CIEy similar to 0.07) based on phenanthroimidazole: Remarkable substitution effects at the N1 position of imidazole on the excited states and electroluminescence properties

Organic light emitting diodes (OLEDs) has shown great potential (light weight, fast response time, flexible and energy efficient) and emerging technology for next-generation display and lighting application. In any case, achieving efficient blue electroluminescence still remains a challenge. Herein, two new deep blue phenanthroimidazole (A) and triphenylamine (D) based fluorophores, N,N-diphenyl-4'-(1-(p-tolyl)-1H-phenanthro [9,10-d]imidazole-2-yl)-[1,1'-biphenyl]-4-amine (4-PIPTPA) and N,N-diphenyl-4'-(1-(4-(trifluoromethyl) phenyl)-1H-phenanthro [9,10-d]imidazole-2-yl)-[1,1'-biphenyl]-4-amine (4-PIPCFTPA) were designed and synthesized. The fluorophores were structurally characterized by spectroscopic methods. These fluorophores are tharmally stable with thermal decomposition temperature (T-d) of similar to 446 degrees C. The photophysical, electronic (theoretical), electrochemical (CV), and electroluminescene properties were thoroughly investigated, the N1 substituted moieties are play a vital role as it affects the photophysical as well as electronic properties of the synthesized fluorophores. Hence, we fabricated undoped and doped devices with newly synthesized emitters and observed that the 4-PIPCFTPA demonstrated the superior performance as compared to that of 4-PIPTPA. The best electroluminescence performance is displayed by the device fabricated with 4-PIPCFTPA (1 wt% in the CBP host) and (3 wt% in the CBP host) with a maximum external quantum efficiency (EQE) of 2.7 and 2.9%, respectively and CIE coordinates of (0.17, 0.07) and (0.18, 0.12) were observed, respectively. The observed EL properties of emitters reveal its potential as efficient deep blue emitters for display applications.

Automated summary

OLEDs have shown great potential as a lightweight, fast response time, flexible, and energy-efficient technology for next-generation display and lighting applications. However, achieving efficient blue electroluminescence remains a challenge. Two new deep blue fluorophores were designed and synthesized, showing potential for display applications.