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      Structurally robust phosphorescent [Pt(O^N^C^N)] emitters for high performance organic light-emitting devices with power efficiency up to 126 lm W−1 and external quantum efficiency over 20%

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          Abstract

          Practical strongly phosphorescent platinum( II) green to white OLED emitters with bulky tetradentate O^N^C^N ligands.

          Abstract

          A series of robust, bulky and strongly emissive platinum( ii) complexes supported by tetradentate O^N^C^N ligands with tert-butyl groups ( 1–4), a bridging tertiary amine ( 5) or a biphenyl group with a spiro linkage ( 6) at the periphery of the [O^N^C^N] ligand scaffold have been prepared. Their photophysical properties were examined by absorption and emission spectroscopy, density functional theory calculations, and ultra-fast time-resolved emission measurements. These complexes display emission quantum yields of up to 95%, with emission maxima λ max in the range of 522 to 570 nm, and have a good thermal stability of up to T d > 423 °C. Notably, the k q values of 4–6 are in the range of 8.5 × 10 6 to 2.0 × 10 7 mol −1 dm 3 s −1, smaller than those (∼10 8 to 10 9 mol −1 dm 3 s −1) of other reported Pt( ii) complexes. The bulky groups at the periphery of the [O^N^C^N] ligand disfavour intermolecular interactions and hence excimer formation in solutions. These complexes are good light-emitting materials (dopants) for OLEDs, since the triplet–triplet annihilation (TTA) and concentration quenching effect arising from intermolecular interactions can be minimized even at a high dopant concentration. The efficiency of the devices fabricated with 4–6 increased with dopant concentration up to a high level of 10% with no extra emitting component or significant shift in the CIE observed. The maximum power efficiency (PE) values achieved for the 5 (yellow-emitting) and 6 (green-emitting) based devices were 118 and 126 lm W −1, respectively. These PE values are the highest among the reported Pt( ii)-OLEDs and comparable to those of the best reported Ir( iii)-OLEDs without the out-coupling technique. Complex 7 is structurally analogous to, but less bulky than 3–6 and is prone to giving excimer emission in the solid state. A high PE of up to 55.5 lm W −1 and external quantum efficiency of up to 25.1% have been realized in the white OLEDs fabricated with 7 as a single emitting material. These values are comparable with those of the best reported WOLEDs based on a single emitting material.

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          Most cited references33

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          Spiro compounds for organic optoelectronics.

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            Electroluminescence from triplet metal—ligand charge-transfer excited state of transition metal complexes

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              Measuring the Efficiency of Organic Light-Emitting Devices

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                Author and article information

                Journal
                CSHCBM
                Chem. Sci.
                Chem. Sci.
                Royal Society of Chemistry (RSC)
                2041-6520
                2041-6539
                2014
                2014
                : 5
                : 12
                : 4819-4830
                Affiliations
                [1 ]State Key Laboratory of Synthetic Chemistry
                [2 ]HKU-CAS Joint Laboratory on New Materials, and Department of Chemistry
                [3 ]The University of Hong Kong
                [4 ]Hong Kong SAR, China
                [5 ]State Key Laboratory on Integrated Optoelectronics
                [6 ]HKU Shenzhen Institute of Research and Innovation
                [7 ]School of Chemistry and Chemical engineering
                [8 ]GuangDong Aglaia Optoelectronic Materials Co., Ltd
                [9 ]China
                [10 ]State Key Laboratory of Luminescent Materials and Devices (South China University of Technology)
                [11 ]Institute of Polymer Optoelectronic Materials and Devices
                [12 ]South China University of Technology
                [13 ]Guangzhou 510640, China
                Article
                10.1039/C4SC01105H
                beb3e426-a6e1-47a7-afdf-636efecc4347
                © 2014
                History

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