Revealing the role of 1,2,4-triazolate fragment of blue-emitting bis-tridentate Ir(III) phosphors: photophysical properties, photo-stabilities, and applications

Novel bis-tridentate Ir(III) complexes are of great interest in the development of blue-emitting organic light-emitting diodes (OLEDs) due to their rigid and robust molecular architecture. In this work, both the functional 6-pyrazolyl-2-phenoxypyridine (pzyPx) and 6-(1,2,4-triazolyl)-2-phenoxypyridine (tazPx) were used as chromophoric chelates in the construction of the blue-emitting Ir(III) phosphors. Accordingly, the substitution of pzyPx with tazPx chelates retains the desired characteristics, i.e. both high quantum yields (>92%) in solution and shortened radiative lifetime (tau(rad)) (from 19.8 to 2.5 ms), respectively. The theoretical calculation reveals that the triazolate moiety contributes considerably to the radiative transition, to which the greater iridium involvement in T-1 -> S-0 transition of tazPx-based complex is responsible for the shortened tau(rad). Consequently, enhanced photostabilities in degassed toluene and competitive performances with maximum EQE of 19.2% with CIE coordinates of (0.17, 0.22) were observed from the tazPx-based complex Px-33. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Novel bis-tridentate Ir(III) complexes with 6-(1,2,4-triazolyl)-2-phenoxypyridine (tazPx) as chromophoric chelates show improved photostabilities and competitive performances in blue-emitting organic light-emitting diodes, with high quantum yields and shortened radiative lifetime compared to complexes using other chelates. Theoretical calculations reveal the significant contribution of the triazolate moiety to the radiative transition, leading to enhanced performance of the tazPx-based complex.