High-Efficiency Red Electroluminescence Based on a Carbene–Cu(I)–Acridine Complex

Abstract

How to develop efficient red-emitting organometallics of earth-abundant copper­(I) is a formidable challenge in the field of organic light-emitting diodes (OLEDs) because Cu­(I) complexes have weak spin-orbit coupling and a serious excited-state reorganization effect. Here, a red Cu­(I) complex, MAC*-Cu-DPAC, was developed using a rigid 9,9-diphenyl-9,10-dihydroacridine donor ligand in a carbene-metal-amide motif. The Cu­(I) complex achieved satisfactory red emission, a high photoluminescence quantum yield of up to 70%, and a sub-microsecond lifetime. Thanks to a linear geometry and the acceptor and donor ligands in a coplanar conformation, the complex exhibited a high horizontal dipole ratio of 77% in the host matrix, first demonstrated for coinage metal­(I) complexes. The resulting OLEDs delivered high external quantum efficiencies of 21.1% at a maximum and 20.1% at 1000 nits, together with a red emission peak at ∼630 nm. These values represent the state-of-the-art performance for red-emitting OLEDs based on coinage metal complexes.

Diversity of Luminescent Metal Complexes in OLEDs: Beyond Traditional Precious Metals

“…The green OLEDs based on Cu(I) and Au(I) attained high EQEs of 23% [16f] and 27%, [23] respectively. The red OLEDs for Cu(I) complexes as emitter also showed high EQE of 21% [25h] . Nevertheless, the EQE of blue OLEDs based on d 10 metal complexes is nowhere near that of green and red counterparts.…”

“…Very recently, Gong et al. reported an efficient red two‐coordinate CMA Cu(I) complexes (Cu49) by introducing 9,9‐diphenyl‐9,10‐dihydroacridine instead of carbazole, because of more rigid molecular structure, stronger electro‐donating ability, and potential large anisotropy when linked to a suitable acceptor unit [25h] . As the result, the red emission with high PLQY of around 70% and high horizontal transition dipole ratio of 77% were achieved for Cu49, endowing the highest EQE of 21.1% with teeny efficiency roll off in OLEDs.…”

Toward rational design of TADF two-coordinate coinage metal complexes: understanding the relationship between natural transition orbital overlap and photophysical properties

“…[19][20][21][22][23][24] Recently, a significant advance in Cu (I) -based TADF materials was achieved using twocoordinate complexes with a carbene ligand to serve as an acceptor and an amide ligand as a donor. [25][26][27][28][29][30][31][32][33][34][35][36] In addition to the copper complexes, isoelectronic silver and gold based complexes have been shown to give highly efficient TADF. 31,[36][37][38] Here we will refer to the (carbene)M(amide) family of complexes as cMa for M = Cu (I) , Ag (I) and Au (I) .…”

Copper(I) Complex as Sensitizer Enables High‐Performance Organic Light‐Emitting Diodes with Very Low Efficiency Roll‐Off

“…[22,23] Luminescent carbene-metal-amide complexes, in which the metal center acts as the π bridge to link the carbene acceptor ligand with the amide donor ligand, have recently emerged as the attractive metal-based TADF emitters for the superiority of high photoluminescence quantum yields (PLQYs) and sub-microsecond lifetimes. [24][25][26] In comparison with the conventional purely organic TADF emitters, the introduction of metal center can dramatically enhance the spinorbital coupling (SOC) and maintain distinct TADF property in the meantime. [27,28] Accordingly, the carbene-metal-amide complexes usually have very quick k RISC (≈10 7 s −1 ) (Figure 1b), making them promising candidates as TADF sensitizers.…”