Efficient yellow electroluminescence of four iridium(iii) complexes with benzo[d]thiazole derivatives as main ligands

Abstract

Four bis-cyclometalated iridium(iii) complexes, (bt)2Ir(tpip), (fbt)2Ir(tpip), (cf3bt)2Ir(tpip) and (dfbt)2Ir(tpip) (bt = 2-phenylbenzo[d]thiazole, fbt = 6-fluoro-2-phenylbenzo[d]thiazole, cf3bt = 2-phenyl-6-(trifluoromethyl)benzo[d]thiazole, dfbt = 5,7-difluoro-2-phenylbenzo[d]thiazole, tpip = tetraphenylimidodiphosphinate) have been synthesized and investigated. All complexes emit yellow light peaks at 564-574 nm with quantum efficiencies (Φem) of 27.1-48.4% and excited state lifetimes of 2.40-2.81 μs in degassed CH2Cl2 solution at room temperature. Correspondingly, organic light-emitting diodes (OLEDs) using these complexes as emitters achieve yellow electrophosphorescence with good device characteristics. Due to its highest photoluminescence quantum yield (48.4%), the device based on (dfbt)2Ir(tpip) displays the best device performance with a maximum current efficiency (ηc, max) of up to 69.8 cd A-1 and a maximum external quantum efficiency (EQEmax) of up to 24.3%. Furthermore, all devices showed low efficiency roll-off ratios. The EQE could still be retained at 17.7%, 16.4%, 18.3% and 20.6% for four devices at a luminance of 1000 cd m-2. These results suggest that these materials have potential application in efficient OLEDs.

Tunable Emission Color of Iridium(III) Complexes with Phenylpyrazole Derivatives as the Main Ligands for Organic Light-Emitting Diodes

“…Their crystallographic data and structure refinement details are listed in Table S1; the selected bond lengths and bond angles are listed in Table S2. As shown in Figure , the coordination geometry of the iridium center in each complex is a distorted octahedral geometry with cis -C,C, cis -O,O, and trans -N,N chelate disposition . The lengths of Ir–C and Ir–N bonds are in the range of 1.978(1)–2.010(1) and 1.938(1)–2.048(1) Å, respectively, close to those in previously reported Ir­(III) complexes .…”

New yellow/orange-emitting heteroleptic iridium(III) complexes with 5,7-difluoro-2-phenylbenzothiazole ligand

“…5,7-Difluoro-2-phenylbenzo[d]thiazole (dfbt) and the corresponding dichloro-bridged [Ir(dfbt) 2 Cl] 2 were synthesized according to our previous literature. 23 1 H NMR spectra were recorded on a Bruker AM 400 MHz instrument, and chemical shifts were reported in ppm relative to Me 4 Si as internal standard. MALDI-TOF-MS spectra were recorded on a Bruker Autoflex II TM Table 2.…”

“…16,22 In 2018, we reported a series of yellow-emitting fluorinated bt-based iridium (III) complexes with tetraphenylimidodiphosphinate (tpip) as ancillary ligand. 23 Among them, the quantum yield of 5,7-positions fluorinated bt-based iridium (III) complex [(dfbt) 2 Ir(tpip)] is the highest one (48.4%). The device based on (dfbt) 2 Ir(tpip) displays the best device performance with a maximum current efficiency (η c, max ) of up to 69.8 cd A −1 and a maximum external quantum efficiency (EQEmax) of up to 24.3%.…”

Influential effect of C^N ligands containing O, S, and Se heteroatoms in the color tuning of four phosphorescent Ir(III) complexes

“…Therefore, it encouraged us to seek more information about the role of the three heteroatoms in iridium complexes. For comparison, we chose the well-known 2-phenylbenzoxazole (bo) [28,29] and 2-phenylbenzothiazole (bt) [30,31] as counterpoints. Specifically, in order to obtain efficient luminescent iridium complexes, bis(diphenylphorothioyl) amide (S-tpip) derivatives containing polar P=S bonds and phenyl rings were used as ancillary ligand due to good stability and strong electron mobility [32].…”