Thermally Activated Delayed Fluorescence Material as Host with Novel Spiro‐Based Skeleton for High Power Efficiency and Low Roll‐Off Blue and White Phosphorescent Devices |
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Authors: | Ya‐Kun Wang Qi Sun Sheng‐Fan Wu Yi Yuan Qian Li Zuo‐Quan Jiang Man‐Keung Fung Liang‐Sheng Liao |
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Affiliation: | Jiangsu Key Laboratory for Carbon‐Based Functional Materials and Devices, Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, China |
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Abstract: | Efficiency roll‐off in blue organic light‐emitting diodes especially at high brightness still remains a vital issue for which the excitons density‐dependent mechanism of host materials takes most responsibility. Additionally, the efficiency roll‐off leads to high power consumption and reduces the operating lifetime because higher driving voltage and current are required. Here, by subtly modifying the triphenylamine to oxygen‐bridged quasi‐planar structure, a novel thermally activated delayed fluorescence type blue host Tri‐o‐2PO is successfully developed. Efficiency roll‐off based on Tri‐o‐2PO is ultralow with external quantum efficiency (EQE) just dropping by around 2% in the high luminance range from 1000 cd m?2 to 10 000 cd m?2. As expected, low turn‐on voltage (≈2.9 V) of device is also achieved, which is close to the theory limit value (≈2.62 V). Super‐high power efficiency (≈60 lm W?1) and EQE (>22%) are also achieved when utilizing Tri‐o‐2PO as host. Furthermore, two‐color warm‐white light with CIE of (0.45, 0.43) and correlated color temperature of 2921 K is also fabricated and a champion EQE of 21% is delivered. These excellent performances prove the strategy of bridging the triphenylamine to reduce ΔEst is validated and suggest the great potential of this novel skeleton. |
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Keywords: | efficiency roll‐off organic light‐emitting diodes (OLEDs) power efficiency (PE) thermally activated delayed fluorescence (TADF) |
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