Synthesis and characterization of new yellow emitting mixed heteroleptic Ir(III) complexes with solution-processed phosphorescent organic light-emitting diodes

Abstract

Two new yellow emitting heteroleptic Ir(III) complexes are designed and synthesized for solution-processed yellow phosphorescent organic light-emitting diodes (PHOLEDs) with the amide-bridge core as main ligand and 2-phenylpyridine (ppy) as the ancillary ligand, named as bis[5-(2-ethylhexyl)−8-(trifluoromethyl)benzo[c][1,5]naphthyrid in-6(5)one](phenylpyridine)iridium(III) (Ir-1) and bis[5-(2-ethylhexyl)benzo[c][1,5naphthyridin-6(5H)one](phenylpyridi ne)iridium(III) (Ir-2). Ir-1 and Ir-2 complexes emit bright yellow emission in dichloromethane solution at 298 K. The newly synthesized Ir(III) complexes reveals the higher quantum yields over 40% and relatively short triplet lifetimes (0.12–0.15 μs), both which warrant to both complexes highly electroluminescence active materials. Both Ir(III) complexes were utilized as emitters for yellow solution-process PHOLEDs and obtained better performance. In particular, maximum external quantum efficiency (EQE_max) and maximum current efficiency (CE_max) of of 13.38% and 39.54 cd A⁻¹ with the CIE (x, y) coordinates of (0.45, 0.53) was achieved for Ir-1 based yellow device. Furthermore, PHOLEDs with Ir-2 as an emitter attained EQE_max of 11.71% and CE_max of 37.60 cd A⁻¹ with good color purity.

Keywords:

• PLQY
• redshift
• solution-process PHOLEDs
• yellow Ir(III) complexes

Additional information

Funding

This work was supported by a grant fund from the National Research Foundation (NRF- NRF-2018R1A5A1025594) by the Ministry of Science, ICT of Korea.