We thank the University of St Andrews for support. EZ-C thanks the Leverhulme Trust for financial support (RPG-2016-047). and the EPSRC (EP/P010482/1) for financial support.

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Purely Organic Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes.

Two metallacages containing Pt(II) phosphine centres bridged by organic donors are shown to display dynamic emission behaviour across a range of concentrations. At low concentrations, the individual cages emit. At high concentrations, or on introduction of additional solvents, aggregation occurs that manifests in colour-tunable fluorescence and white-light emission in THF.

Highly emissive platinum( II ) metallacages

Efficiency is crucial for organic light emitting diodes (OLEDs) to be energy-saving and to have a long lifetime for display and solid state lighting applications. Numerous approaches have been proposed to attain high efficiency OLEDs through the synthesis of novel organic materials, the design of light extraction structures and the design of efficiency-effective device architectures. In this report, we first summarise the efficiency records of OLED devices using fluorescent, phosphorescent, and thermally activated delay fluorescent materials. Importantly, we review all the available efficiency-effective device architectural approaches, which include using thin layer structures, low carrier injection barriers, high carrier mobility, balanced carrier injection, effective carrier confinement, effective host-to-guest energy transfer, effective recombination zone, effective exciton generation on the host, effective exciton confinement, p–i–n structures, and tandem structures. It is hoped that better device structures can therefore be devised upon suitable device engineering to achieve higher efficiency for OLED devices.

Approaches for fabricating high efficiency organic light emitting diodes

Blue organic light-emitting diodes (OLEDs) can play a critical role in the field of organic electroluminescence (EL). As the most important applications of OLEDs, both new generation full-color flat-panel displays and future energy-saving solid-state lighting sources require blue color EL to fulfill their functions properly. However, considerable challenges still exist in searching for highly efficient, color stable, and long-lifespan materials and devices that emit blue color, especially in the development of deep-blue emitters, which are indispensable for high-quality displays and lighting sources. Encouragingly, great progress has been made in the area of deep-blue OLEDs in recent years with continuous efforts made by scientists, who are responsible for the significant achievements in the field of OLEDs. Hence, in this review, the crucial tactics employed to obtain high performance deep-blue emitters are presented, including polymers, dendrimers, small organic molecules, delayed fluorescent systems, and phosphorescent emitters. Moreover, the future perspectives and ongoing challenges of this research frontier are also highlighted.

Recent advances of the emitters for high performance deep-blue organic light-emitting diodes

Organic light-emitting diodes (OLEDs) are increasingly used in displays replacing traditional flat panel displays; e.g., liquid crystal displays. Especially, the paradigm shifts in displays from rigid to flexible types accelerated the market change from liquid crystal displays to OLEDs. However, some critical issues must be resolved for expansion of OLED use, of which blue device performance is one of the most important. Therefore, recent OLED material development has focused on the design, synthesis and application of high-efficiency and long-life blue emitters. Well-known blue fluorescent emitters have been modified to improve their efficiency and lifetime, and blue phosphorescent emitters are being investigated to overcome the lifetime issue. Recently, thermally activated delayed fluorescent emitters have received attention due to the potential of high-efficiency and long-living emitters. Therefore, it is timely to review the recent progress and future prospects of high-efficiency blue emitters. In this feature article, we summarize recent developments in blue fluorescent, phosphorescent and thermally activated delayed fluorescent emitters, and suggest key issues for each emitter and future development strategies.

Recent Progress in High‐Efficiency Blue‐Light‐Emitting Materials for Organic Light‐Emitting Diodes

Organic light-emitting diodes (OLEDs) are competitive candidates for the next generation flat-panel displays and solid state lighting sources. Efficient blue-emitting materials have been one of the most important prerequisites to kick off the commercialization of OLEDs. This tutorial review focuses on the design of blue fluorescent emitters and their applications in OLEDs. At first, some typical blue fluorescent materials as dopants are briefly introduced. Then nondoped blue emitters of hydrocarbon compounds are presented. Finally, the nondoped blue emitters endowed with hole-, electron- and bipolar-transporting abilities are comprehensively reviewed. The key issues on suppressing close-packing, achieving pure blue chromaticity, improving thermal and morphological stabilities, manipulating charge transporting abilities, simplifying device structures and the applications in panchromatic OLEDs are discussed.

Minrong Zhu

Papers

Blue fluorescent emitters: design tactics and applications in organic light-emitting diodes

Blue Fluorescent Emitters: Design Tactics and Applications in Organic Light-Emitting Diodes