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Degradation of Ir based blue phosphorescent emitters was analyzed from the viewpoint of triplet-polaron annihilation (TPA) of the emitters. Two different classes of Ir emitters, F substituted phenylpyridine type Ir emitter and F substituted phenylimidazole type Ir emitter, were compared as the blue emitters. Aging test of singlet carrier devices of the Ir emitters under polaron, exciton, and exciton-polaron revealed that the phenylimidazole type Ir emitter was relatively more resistant to the TPA degradation than the phenylpyridine type Ir emitter and extended the lifetime of blue phosphorescent organic light-emitting diodes. In addition, the lifetime and degradation of the short-living blue phosphorescent devices were improved by the host material suppressing the TPA under negative polaron using an electron scattering emitting layer structure. [ABSTRACT FROM AUTHOR]

We report fluorenyl amine-based electron blocking layers (EBLs) N,9,9-triphenyl-N-(4′-(triphenylsilyl)-[1,1′-biphenyl]−4-yl)−9 H-fluoren-2-amine (P-pSi-DPFA), N,9,9-triphenyl-N-(3-(triphenylsilyl)phenyl)−9 H-fluoren-2-amine (P-mSi-DPFA), and N-([1,1′-biphenyl]−4-yl)−9,9-diphenyl-N-(3-(triphenylsilyl)phenyl)−9 H-fluoren-2-amine (BP-mSi-DPFA) that prevent intermolecular interactions with emissive layer (EML). Triplet-triplet fusion (TTF)-based organic light-emitting diodes (OLEDs) use anthracene derivatives as hosts, and due to the electron-rich nature of anthracene core, the recombination zone is predominantly formed at the EBL/EML interface. Therefore, it is important to control the intermolecular interaction between EBL and EML while also having an EBL with suitable hole transport characteristics and an appropriate highest occupied molecular orbital (HOMO) level. We developed TTF-based OLED achieving up to 1489 hours (LT 50 at 500 cd/m2) using P-pSi-DPFA as the EBL, securing hole transport characteristics through a fluorenyl amine core, and preventing unwanted intermolecular interactions with the EML by substituting triphenyl silane into the amine core. • Three newly synthesized EBL materials extended OLED device lifetime significantly. • Experimental and theoretical analyses support EBL materials' effectiveness. • P-pSi-DPFA device achieved an impressive 1489-hour lifetime at 500 cd/m². [ABSTRACT FROM AUTHOR]

High triplet energy exciplex hosts are developed using new electron transport type hosts with triphenylsilyl blocking groups to obtain high solid state triplet energy and exciplex triplet energy. Two triphenyltriazine derived hosts, 2‐phenyl‐4,6‐bis(4‐(triphenylsilyl)phenyl)‐1,3,5‐triazine (pSiTrz) and 2‐phenyl‐4,6‐bis(3‐(triphenylsilyl)phenyl)‐1,3,5‐triazine (mSiTrz), are synthesized as the high triplet energy hosts with electron transport properties. The two hosts show high triplet energy over 2.90 eV both in solution and solid film, and afford high triplet energy over 2.90 eV in the mixed hosts with a hole transport type 2,2′‐di(9H‐carbazol‐9‐yl)‐1,1′‐biphenyl (oCBP) host. The doping of a deep blue phosphorescent emitter in the mixed host oCBP:mSiTrz achieves high external quantum efficiency over 20% with a color coordinate of (0.14, 0.16) and device lifetime of longer than 1000 h at 100 cd m‐2. This is the first demonstration of simultaneous achievement over 20% external quantum efficiency (EQE) and 1000 h lifetime in the deep blue organic light‐emitting diodes with a x+y color coordinate value below 0.30. [ABSTRACT FROM AUTHOR]

Comprehensive study to understand the degradation mechanism of high efficiency blue organic light-emitting diodes by charge transport layers was carried out by managing the device parameters and charge transport materials. Although it has been generally accepted that the charge transport layers are important for long lifetime, the degradation mechanism was not clear. From this work, it was revealed that exciton quenching of emitters by the degradation products of charge transport layers is the main degradation pathway of blue phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes. It was described that the degradation of the blue devices by the charge transport layers would be largely avoided by separating the exciton generating emitters from the charge transport layers by shifting the exciton formation zone to the center of the emitting layer. Eventually, the lifetime of the blue devices with the emission zone fall apart from the charge transport layers was not affected by the charge transport layers because exciton quenching by the degradation products of the charge transport layers was suppressed. [ABSTRACT FROM AUTHOR]

• Ir(dpbic) 3 works as an intermediate energy carrier (IEC) and p-type host in PhOLEDs. • IEC forms multiple energy transfer channels in PhOLEDs to minimize degradation. • Superbly long lifetime and high efficiency in deep blue phosphorescent OLED for IEC. Despite over two decades of relentless endeavor, the industrial application of blue phosphorescent organic light-emitting diodes (PhOLEDs) has not been realized due to extremely short lifetime. The degradation of PhOLEDs is generally accelerated at high current levels since high triplet energy with long exciton lifetime are mostly concentrated on host molecules and transferred to dopant via slow Dexter energy transfer (DET) processes rather than fast Förster resonance energy transfer (FRET) processes. Herein, we propose a novel device architecture that creates multiple energy transfer channels by employing an Ir-complex intermediate energy carrier (IEC). Unlike exciplex or electroplex, no excitons were generated between the host and the IEC even though the IEC also behaves as a p-type host. The most crucial role of the IEC is to diversify the energy transfer channels. By introducing the IEC in deep blue PhOLEDs, both FRET and DET channels were additionally created between the IEC and the host, and the IEC and the dopant. Consequently, an unprecedentedly long half luminance lifetime of 13,830 h at an initial luminance of 100 cd/m2 was obtained with a high efficiency of 14.4% and CIEy = 0.17. To our best knowledge, the lifetime in our report is the longest with a deep blue phosphorescent Ir complex. [ABSTRACT FROM AUTHOR]