Bipolar Blue Host Emitter with Unity Quantum Yield Allows Full Exciton Radiation in Single-Emissive-Layer Hybrid White Organic Light-Emitting Diodes

Abstract

Phosphorescence/fluorescence hybrid white organic light-emitting diodes (OLEDs) are highly appealing for solid-state lighting. One major challenge is how to fully utilize the electrically generated excitons for light output. Herein, an efficient strategy to realize full exciton radiation is successfully revealed by a judicious molecular design and suitable device engineering. A blue host emitter TP-PPI is designed and synthesized, exhibiting a near 100% photoluminescence quantum yield and a high triplet energy level, enabling high-performance blue fluorescence and sensitization of a yellow phosphorescent dopant. Full exciton radiation in hybrid white OLEDs is demonstrated with a single emitting layer formed by doping a yellow phosphor (PO-01) into TP-PPI. Near 100% exciton utilization and state-of-the-art external quantum efficiency of 27.5% are achieved with the high-efficiency blue-emitting host and an electron-trap engineered device architecture.

Hybridized Local and Charge-Transfer Excited-State Fluorophores through the Regulation of the Donor–Acceptor Torsional Angle for Highly Efficient Organic Light-Emitting Diodes

“…14,15 Given the fact that the HLCT concept was proposed a few years ago, to date the development of HLCT emitters still lags behind TADF emitters. [16][17][18] In particular, device performances of most HLCT-based OLEDs remain restricted as their external quantum efficiencies (EQEs) are generally <10%, 10,15,[19][20][21][22][23] leaving much room for efficiency improvement. Seen in this light, there is an urgent need for simple and effective strategies to develop high-efficiency HLCT emitters and related OLEDs.…”

Disentangling Multiple Effects on Excited‐State Intramolecular Charge Transfer among Asymmetrical Tripartite PPI‐TPA/PCz Triads

“…[20][21][22] Recently, much work has been done with the phenanthroimidazole (PI), unit which has demonstratedt hat the PI group is as uitable choicea st he central moiety of deep-blue emitters. [23,24] When N1 and C2 positions of PI are modified with ab enzene ring, one of the most commona nd typical derivatives, namely 1,2diphenylphenanthroimidazole (PPI, Scheme 1) is obtained. [25,26] PPI is an itrogen-containing heterocyclic conjugate group with ar igid planar conjugated structure having excellent properties, such as high fluorescenceq uantum yield and wide light absorption, whichm ake it very attractive for employment as a buildingb lock for the preparation of blue emitters.…”

“…For display applications, blue emission plays a crucial role in organic electroluminescence (EL); it not only acts as one of the red–green–blue primary colors, but also can integrate low‐energy‐phosphorescence emitters to form hybrid white organic LEDs [20–22] . Recently, much work has been done with the phenanthroimidazole (PI), unit which has demonstrated that the PI group is a suitable choice as the central moiety of deep‐blue emitters [23, 24] . When N1 and C2 positions of PI are modified with a benzene ring, one of the most common and typical derivatives, namely 1,2‐diphenylphenanthroimidazole (PPI, Scheme 1) is obtained [25, 26] .…”

Versatile Host Materials for Highly‐Efficient Green, Red Phosphorescent and White Organic Light‐Emitting Diodes

“…In the past decades, organic light-emitting diodes (OLEDs) have become increasingly irreplaceable for their excellent potential in commercial full-color flat panel displays and general lighting applications. [1][2][3][4][5] In general, traditional fluorescent OLEDs have been widely used in commercial devices due to their advantages of high color purity and long operational lifetime. However, they can only harvest excitons in the singlet state, which is equal to 25 % of all the electronically generated excitons.…”