High performance blue-green and green phosphorescent OLEDs based on iridium complexes with N^C^N-coordinated terdentate ligands

Abstract

Graphical Abstract:Series of highly efficient phosphorescent organic light-emitting diodes (PhOLEDs) based on two iridium complexes (1 and 2) constructed by the N^C^N-coordinated terdentate ligands have been achieved. They exhibit the high peak power efficiency (PE) and external quantum efficiency (EQE) values of 35.5 lm W −1 & 15.8 % for blue-green emission, 47.4 lm W −1 & 16.7 % for green emission, which maintain the high level of 19.2 lm W −1 & 14.5 % and 30.6 lm W −1 & 16.1 % at rather high and practical luminance of 500 cd m −2 with the low driving voltages of less than 6 V. The appropriate selection of a prominent electron-transport molecule TPBi as a host to matching the dopant molecules (1 or 2) that possess the obvious hole-transport ability is critical in the remarkable EL-performance improvement on previous reports.Highly efficient phosphorescent organic light-emitting diodes (PhOLEDs) based on two iridium complexes constructed by the N^C^N-coordinated terdentate ligands (also called pincer ligands) have been achieved. They exhibit the high peak power efficiency (PE) and external quantum efficiency (EQE) values of 35.5 lm W −1 & 15.8 % for blue-green emission, 47.4 lm W −1 & 16.7 % for green emission, 10 which maintain the high level of 19.2 lm W −1 & 14.5 % and 30.6 lm W −1 & 16.1 % at rather high and practical luminance of 500 cd m −2 with the low driving voltages of less than 6 V. These values show almost a twofold enhancement over the most efficient PhOLEDs based on the pincer iridium complexes ever reported. Here, the appropriate selection of a prominent electron-transport molecule TPBi as a host to matching the dopant molecules (1 or 2) that possess sufficient hole-transport ability is critical in the 15 remarkable EL-performance improvement on previous reports. We will present a comprehensive investigation that not only encompasses the conventional thermal, photophysical and electrochemical properties of both complexes, but also emphatically studies the charge carrier injecting/transporting and electroluminescent (EL) characteristics of two phosphorescent emitters doped in different host.

Sky Blue-Emitting Iridium(III) Complexes Bearing Nonplanar Tetradentate Chromophore and Bidentate Ancillary

“…Parallel to the development of tris-bidentate metal complexes, there is a growing interest of using multidentate chelate in assembly of luminescent Ir­(III) phosphors. For instance, Williams, Haga, and others − have examined tridentate cyclometalate in constructing Ir­(III) complexes bearing ligands arranged in three distinctive coordination mode, that is, so-called 3 + 2 + 1 mode, in which the planar tridentate chelate adopted a meridional coordination arrangement, cf. [Ir­(dpyx)­(dfppy)­Cl] (Scheme ).…”

Fine Emission Tuning from Near-Ultraviolet to Saturated Blue with Rationally Designed Carbene-Based [3 + 2 + 1] Iridium(III) Complexes

“…) are attributed to the mixture of spin-allowed metalto-ligand charge transfer ( 1 MLCT) transitions from the iridium(III) core to the pbib or C^C ligands, singlet ligandcentered ( 1 IL), or ligand-to-ligand charge-transfer transitions ( 1 LLCT). 56 The absorption tails beyond ca. 340 nm (ε < 9.1 × 10 3 M −1 cm −1 ) are mainly assigned as the triplet metal-to-ligand and intraligand charge transfer ( 3 MLCT and 3 ILCT) transitions.…”

“…In general, no obvious reduction wave or couple was recorded within the solvent window, similar to the previously reported structurally related [3 + 2 + 1] coordinated iridium(III) complexes. 56 While a quasi-reversible first oxidation wave at ca. +1.15 V versus The saturated calomel electrode (SCE) was found for [(pbib)Ir-(dbfmi)CN] and [(pbib)Ir(dbthmi)CN], an irreversible oxidation peak at +1.07 to +1.20 V versus the SCE was found for the other complexes.…”

Highly Efficient Phosphorescent Blue-Emitting [3+2+1] Coordinated Iridium (III) Complex for OLED Application

“…The absorption bands with small vibrational shoulders at 300-330 nm were ascribed to spinallowed intra-ligand ( 1 π→π*) transition and metal to ligand charge transfer ( 1 MLCT) transitions. The weak absorptions bands (ε ≈ 0.3 × 104 M −1 cm −1 ) lying in the visible light region at 350-400 nm were related to the spin-orbit coupling enhanced 3 π→π* states and spin-forbidden metal to ligand charge transfer ( 3 MLCT) transitions (Chen et al, 2015). The PL spectra of Ir-dfpMepy-CN exhibited strong phosphorescent emission at around 430-470 nm with maximum peaks at 440 and 466 nm, which should be attributed to the 3 MLCT 3 LLCT, 3 LC induced by spin-orbit coupling.…”