4 years ago

White Organic LED with a Luminous Efficacy Exceeding 100 lm W−1 without Light Out-Coupling Enhancement Techniques

White Organic LED with a Luminous Efficacy Exceeding 100 lm W−1 without Light Out-Coupling Enhancement Techniques
Jiao-Jiao Liang, Ya-Kun Wang, Chen-Chao Huang, Si-Hua Li, Sheng-Fan Wu, Man-Keung Fung, Qi Sun, Liang-Sheng Liao
Luminous efficacy (LE), which is given by the ratio of luminous flux to power, is commonly used to measure the power consumption of a light source. Unfortunately, the LE of white organic light-emitting diodes (OLEDs) still lags behind those of inorganic LED for practically used (>100 lm W−1). In this paper, an ultraefficient white OLED is discussed based on a newly designed thermally activated delayed fluorescent exciplex host. The resulting white OLED delivers an unusually high forward-viewing LE of 105.0 lm W−1 and external quantum efficiency (EQE) ηext of ≈30% (without using any optical out-coupling techniques). As far as it is known, specifically, these efficiencies are the highest values among the published white OLEDs to date. Two-color warm white emission is realized with Commission International de I'Eclairage coordinates of (0.40, 0.48) at a brightness of 1000 cd m−2. Furthermore, the well-matched energy alignment endows the device with an extremely low turn-on voltage (≈2.5 V). Such high efficiencies and excellent device performance should benefit from the advantages of exciplex material solely used as the host. Therefore, this study anticipates that the findings have great potential to boost the LE of OLEDs, and more importantly, fulfill the power efficacy requirement for lighting applications. An outstanding blue exciplex, named mCP:B4PyMPM, is implemented as a host for white organic light-emitting diode (OLED). Super-high luminous efficacy of 105.0 lm W−1 and external quantum efficiency of >28% are realized without employing optical out-coupling techniques. Efficiency roll-off of mCP:B4PyMPM based OLEDs is relatively mild. Additionally, extremely low turn-on voltages (≈2.5 V) and warm white emission are also achieved.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adfm.201701314

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