Shine bright or live long: substituent effects in [Cu(N^N)(P^P)]⁺-based light-emitting electrochemical cells where N^N is a 6-substituted 2,2′-bipyridine

Abstract

Copper-based LECs with a maximum efficacy of 3.0 cd A−1 (luminance = 145 cd m−2) or with lifetimes >80 h have been achieved.

The effects of introducing sterically demanding aryl substituents in [Cu(N^N)(P^P)]+complexes

“…1,2,3 Building upon the pioneering work of McMillan and coworkers, 4,5 [Cu(N^N)(POP)] + and [Cu(N^N)(xantphos)] + complexes (POP = bis(2-(diphenylphosphino)phenyl)ether, xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene, N^N is an N,N'-chelating ligand) are established as favoured components in the emissive layers in LECs 6,7,8,9,10,11,12,13,14 or organic light-emitting devices (OLEDs). 15,16 Related complexes find application in oxygen sensing, 17 CO 2 reduction, 18 and water reduction.…”

“…19,20 The N^N ligand in [Cu(N^N)(POP)] + and [Cu(N^N)(xantphos)] + is usually a 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) derivative, and the introduction of simple substituents into the 6-and 6'-positions of bpy or 2-and 9-positions of phen modulates the emission properties of the complexes. 4,7,8 We recently demonstrated the remarkable performance of [Cu(N^N)(POP)][PF 6 ] and [Cu(N^N)(xantphos)][PF 6 ] (N^N = 6-methyl-2,2'-bipyridine, 6-ethyl-2,2'-bipyridine or 6,6'-dimethyl-2,2'-bipyridine) in LECs. 8 However, achieving both high efficacy and long device lifetime remains challenging.…”

“…4,7,8 We recently demonstrated the remarkable performance of [Cu(N^N)(POP)][PF 6 ] and [Cu(N^N)(xantphos)][PF 6 ] (N^N = 6-methyl-2,2'-bipyridine, 6-ethyl-2,2'-bipyridine or 6,6'-dimethyl-2,2'-bipyridine) in LECs. 8 However, achieving both high efficacy and long device lifetime remains challenging. A LEC with [Cu(Mebpy)(xantphos))][PF 6 ] in the emissive layer had a lifetime of >15 h and an efficacy of 1.9 cd A -1 .…”

Origin of a counterintuitive yellow light-emitting electrochemical cell based on a blue-emitting heteroleptic copper(i) complex

“…[9][10][11][12][13][14][15][16] This is attributed to their simple and low-cost synthesis, as well as the ease of chemical modifications for fine-tuning their photoluminescence and electrochemical features. In addition, they typically show a two-excited state radiative mechanism that involves the thermal repopulation of the emitting singlet excited state from the lowest-lying triplet state, i.e., thermally activated delayed fluorescence (TADF).…”

“…9,10,15 As prime examples in [Cu(N^N)(P^P)] + LECs, the efficiency and the stability have been enhanced by designing N^N ligands with substituents strategically attached to shield the coordination sphere and/or increasing the planarity of the ligands. 9,[13][14][15][16][22][23][24] These recent achievements pinpoint the great potential of copper(I) complexes to replace complexes based on the much more rare and expensive iridium(III) in the near future. In this context, the quest for blue LECs based on copper(I) complexes is at the forefront of the field.…”