Transition-Metal Complexes for Triplet–Triplet Annihilation-Based Energy Upconversion

Abstract

In recent years, significant progress has been achieved in the field of triplet-triplet annihilation (TTA)-based energy upconversion, in which transitionmetal complexes as the sensitizers play a key role. These complexes are different from organic fluorophores because the triplet excited states, instead of the singlet excited states, are populated with a high intersystem crossing (ISC) efficiency upon photoexcitation. Meanwhile, the long-lived triplet excited states in the microsecond range are observed for these complexes. All these properties are favorable when transition-metal complexes, including Ir(III), Pd(II), Pt(II), Ru(II), Zn(II), Re(I), Cu(I), and Au(III) complexes summarized herein, are used as sensitizers for TTA upconversion. Moreover, some examples of organic sensitizers and the applications of TTA upconversion systems are also summarized.

A Small Cationic Organo–Copper Cluster as Thermally Robust Highly Photo- and Electroluminescent Material

“…35 Current efficiencies (CE max ) remain typically below 60 cdA -1 , [29][30][31] with occasionally reported peaks between 65-73 cdA -1 . 32,34 Multi-core Cu(I) complexes with rigid geometries are reported to possess bright PL, for instance dinuclear Cu(I) species including halide bridged complexes, 23,[36][37][38][39] halide-free phosphine-bridged complexes, 40 as well as amide-bridged dinuclear complexes. 18,22 Stollenz and co-workers presented luminescent multinuclear copper(I) arrays bridged by bisamidine ligands giving rise to coiled metal chains with close d 10 -d 10 Cu(I) interactions.…”

“…Very recently two-coordinate Cu­(I) complexes with a carbene and amide ligand in coplanar arrangement were reported to suppress nonradiative decay, reaching a remarkable PLQY of up to 99% and EQE max of 9.7%. , The maximum luminance ( L max ) for Cu-based devices ranges commonly between 180 and 17600 cd m –2 , , with peak performances reported between 34 000 and 42 000 cdm –2 . Current efficiencies (CE max ) remain typically below 60 cd A –1 , − with occasionally reported peaks in the range 65–73 cd A –1 . , Multicore Cu­(I) complexes with rigid geometries are reported to possess bright PL, for instance dinuclear Cu­(I) species including halide-bridged complexes, ,− halide-free phosphine-bridged complexes, and amide-bridged dinuclear complexes. , Stollenz and co-workers presented luminescent multinuclear copper­(I) arrays bridged by bisamidine ligands, giving rise to coiled metal chains with close d 10 –d 10 Cu­(I) interactions . Rigid dinuclear amide-bridged Cu­(I) structures with a bulky ligand set were shown to afford narrow fwhm (2400 cm –1 ) owing to a low reorganization energy and hampered solvent ligation in the excited state .…”