Dendritic Carbene Metal Carbazole Complexes as Photoemitters for Fully Solution-Processed OLEDs

Abstract

Light-emitting carbene-metal amide (CMA) complexes bearing first and second generation carbazole dendron ligands are reported, (Ad L)M(G n), (M = Cu and Au; G n carbazole dendrimer generation, where n = 1 and 2; Ad L = adamantyl-substituted cyclic (alkyl)amino)carbene). The thermal stability of the complexes increases with each dendrimer generation. Cyclic voltammetry indicates that the HOMO/LUMO energy levels are largely unaffected by the size of the dendron, while first reduction and oxidation processes show a quasi-reversible character. The gold complexes in toluene at room temperature show photoluminescent quantum yields (PLQYs) of up to 51.5% for the first and 78% for the second generation. Varied temperature transient

Carbene metal amide photoemitters: tailoring conformationally flexible amides for full color range emissions including white-emitting OLED

“…All gold complexes show a quasi-reversible, carbene ligand-centered reduction process similar to our previous reports. 2,13,29 The peak-to-peak separation DE p varies within a small range of 77-91 mV for gold complexes; this is higher than the expected value of 59 mV for a theoretical reversible one-electron process. The oxazine complex Cu6 shows quasireversible reduction with a peak-to-peak separation DE p of 79 mV, whereas other copper complexes Cu1-Cu3 showed irreversible reduction processes.…”

“…Radiative rates exceeding 10 6 s À1 and near unity PLQY values have been realized. [13][14][15] The principle of carbene-metal-amide photoemitters has recently been extended to dendritic systems 29 and to a range of related carbazolate-based CMA systems. [30][31][32] Whereas the studies so far have concentrated on the carbazole ligands, where the amide N-atom is locked into a rigid 5membered ring, we report here a series of CMA complexes carrying amide ligands based on various phenoxazine, phenothiazine, di-and tribenzazepine and sulfone derivatives in which the N-atoms are part of conformationally exible 6-or 7membered rings.…”

Highly efficient blue organic light-emitting diodes based on carbene-metal-amides

“…The emission process involved has been subject to a number of theoretical and spectroscopic investigations; [22][23][24] modelling has shown that upon rotation about the metal-N σ-bond, the ΔE(S1-T1) energy gap decreases and at high twist angles may approach zero. 13, [21][22][23][24] Here we report the synthesis of new Au-bridged emitters which enable blue host-free OLEDs with EQEs of 17.3% (λem,max = 473 nm), as well as host:guest devices with a peak wavelength of 450 nm and an EQE of up to 20.9%. At practical brightness levels of 100 cd m -2 , we achieve EQE = 17.2% and EQE = 17.8 % for the best host-free and host:guest devices, respectively.…”

“…19 These complexes are soluble in most organic solvents and sufficiently thermally stable to enable the fabrication of OLED devices by both solution processing and thermal vapour deposition techniques. 13, [19][20][21] CMAs do not suffer from strong concentration quenching in the solid state, attributed to the lack of close metal-metal contacts, enabling the realization of host-free green devices with an external quantum efficiency (EQE) of 23.1%. 20 Due to the linear two-coordinate geometry, CMAs are conformationally flexible, with a low barrier for rotation about the metal-N σ-bond.…”

“…We therefore prepared the CF3substituted carbazolate complexes 1 (R 1 = CF3, R 2 = t Bu) and 2 (R 1 = R 2 = CF3) ( Figure 1) from ( Ad CAAC)AuCl and the corresponding carbazoles in the presence of KO t Bu, following previously published procedures. [19][20][21] The structural and PL data of the known green (R 1 = R 2 = H, here complex 3) and yellow emitters (R 1 = R 2 = t Bu, here complex 4) are included for comparison. 19 Complexes 1 and 2 were prepared on a 5 g scale as white solids which are stable in air and in solution for long periods of time.…”