Eliminating nonradiative decay in Cu(I) emitters: >99% quantum efficiency and microsecond lifetime

Abstract

Luminescent complexes of heavy metals such as iridium, platinum, and ruthenium play an important role in photocatalysis and energy conversion applications as well as organic light-emitting diodes (OLEDs). Achieving comparable performance from more–earth-abundant copper requires overcoming the weak spin-orbit coupling of the light metal as well as limiting the high reorganization energies typical in copper(I) [Cu(I)] complexes. Here we report that two-coordinate Cu(I) complexes with redox active ligands in coplanar conformation manifest suppressed nonradiative decay, reduced structural reorganization, and sufficient orbital overlap for efficient charge transfer. We achieve photoluminescence efficiencies >99% and microsecond lifetimes, which lead to an efficient blue-emitting OLED. Photophysical analysis and simulations reveal a temperature-dependent interplay between emissive singlet and triplet charge-transfer states and amide-localized triplet states.

Copper(I) Phosphinooxazoline Complexes: Impact of the Ligand Substitution and Steric Demand on the Electrochemical and Photophysical Properties

“…Hence, only in C5 and C7 , where the substituents at adjacent ligands are pointing towards each other, the flattening distortion is hampered (for S 0 and S 1 structures see Figure S10). Another promising alternative to prevent unwanted flattening upon photoexcitation is the design of linear Cu I complexes based on for example, cyclic alkyl(amino)carbenes, N ‐heterocyclic carbenes and different pyridine or amide ligands . The coplanar arrangement of the ligands can suppress non‐radiative decay and reduce structural reorganization resulting in highly efficient Cu I emitters.…”

Synthesis of copper(i) cyclic (alkyl)(amino)carbene complexes with potentially bidentate N^N, N^S and S^S ligands for efficient white photoluminescence

“…24 The 1 H NMR spectrum of this product proved to be identical to that previously reported. 10 Synthesis of ( Me2 CAAC)Cu (…”

“…S1) while more than 300 meV blue-shift is common for ligand-to-ligand CT band in CMA emitters. 2,10 There is a 30 nm red-shift in the low energy absorption band on exchanging the xanthate ligand in 1 for dithiocarbamate in 3. The UV/vis spectrum of the S^N complex 6 is closely similar to…”

“…Linear coinage metal complexes of the type (L)MX based on L = cyclic (alkyl)(amino)carbene ligands (CAACs) have recently emerged as a novel class of light emitting materials due to their ability to act as highly efficient photoemitters in organic light-emitting diodes (OLEDs). [1][2][3][4][5][6][7][8][9][10][11] In most cases the most efficient emitters proved to be complexes where X = aryl amide, and in particular X = carbazolate, giving rise to "carbenemetal-amide", or "CMA" materials. On photochemical or electrochemical excitation these compounds display highly efficient delayed emission, which is due to a charge transfer process involving electron donation from an electron-rich amide ligand to a LUMO based mainly on the carbene p-orbital, which acts as π-electron acceptor.…”

Ultrastable atomically precise chiral silver clusters with more than 95% quantum efficiency

“…This observation is reminiscent of TADF materials (38)(39)(40)(41), where delayed fluorescence is obtained owing to efficient reverse intersystem crossing (RISC) from the lowest triplet excited state (T 1 ) to the lowest singlet excited state (S 1 ). In the past few years, some strategies have been developed to achieve TADF in low-cost Cu(I) and Ag(I) compounds (38)(39)(40)(41). We tentatively assigned the higher energy emission band (556 nm) of Ag 6 L 6 at RT, which crosses over its excitation spectrum ( Fig.…”