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Blue organic light-emitting diodes: current status, challenge, and future outlook

Abstract

The recent progress of efficiency improvement, emission color tuning, and lifetime elongation of blue organic light-emitting diode (OLED) is reviewed. The latter is one of the most important bottlenecks for OLED developments. The current status of blue light-emitting material design with emission mechanisms such as fluorescence (F), phosphorescence (Ph), thermally activated delayed fluorescence (TADF), and hybridized local and charge transfer (HLCT) are introduced in the first part of this review. Compared to red and green devices, the long exciton lifetime of the high energy triplet exciton in a blue OLED is one of the main issues. To avoid the accumulation of high energy triplet excitons in the emitter for blue OLEDs, assisted triplet-triplet fluorescence (TTF) and HyperfluorescenceTM are employed to harvest the triplet excitons. In the second part of this review, we focus on issues from an application viewpoint: What are the requirements of blue OLEDs for display and lighting technologies in terms of efficiency, color, and lifetime? Key performance metrics of blue OLEDs with different technologies over time are summarized. Independent of technology, the trend is similar: external quantum efficiency improves for the first stage of research, followed by color tuning, and then finally lifetime elongation. State-of-art device performances of blue OLEDs with various emission mechanisms are illustrated. Although Ph- and TADF-emission based devices show satisfactory efficiency and electroluminescence (EL) spectrum, despite having a lower efficiency TTF-emission based devices are the mainstream for real application due to their relatively long operation lifetime. Blue Ph-OLEDs have the potential for lighting application with suitable material selection and device design. We collected the published results and tried our best to make a fair comparison in operation lifetime among different technologies. Finally, we discuss possible future outlooks from different viewpoints including new materials, device designs, and applications of blue OLEDs.

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Publication details

The article was received on 11 Jan 2019, accepted on 04 Apr 2019 and first published on 08 Apr 2019


Article type: Review Article
DOI: 10.1039/C9TC00204A
Citation: J. Mater. Chem. C, 2019, Accepted Manuscript

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    Blue organic light-emitting diodes: current status, challenge, and future outlook

    J. LEE, C. Chen, P. Lee, H. Lin, M. Leung, T. Chiu and C. Lin, J. Mater. Chem. C, 2019, Accepted Manuscript , DOI: 10.1039/C9TC00204A

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