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Highly Efficient Hybrid White Organic Light-Emitting Diodes with Single Emission Layer by Solution-Process Jun-Yi Wu, and Show-An Chen ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b14695 • Publication Date (Web): 29 Dec 2017 Downloaded from http://pubs.acs.org on December 29, 2017
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ACS Applied Materials & Interfaces
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Highly Efficient Hybrid White Organic Light-Emitting Diodes with Single
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Emission Layer by Solution-Process
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Jun-Yi Wu and Show-An Chen*
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Chemical Engineering Department and Frontier Research Center on Fundamental and
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Applied Sciences of Matters, National Tsing-Hua University
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Hsinchu 30013, Taiwan, ROC
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*Corresponding author E-mail:
[email protected] 10 thermally
activated
delay
fluorescence
(TADF),
TADF
blue
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Keywords:
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light-emitting diode (TADF BOLED), TADF-Phosphor hybrid white organic light
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emitting diodes (T-P hybrid WOLED), mixed-host, low efficiency roll-off,
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solution-process.
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ABSTRACT
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We use the mixed host, 2,6-bis(3(carbazol9yl)phenyl)pyridine (26DCzPPy)
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blending with 20 wt % tris(4-carbazoyl-9- ylphenyl) amine (TCTA) for lowering
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hole-injection barrier, along with the bipolar and high photoluminescence quantum
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yield
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9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine
(Φp=
84
%)
blue
TADF
1 ACS Paragon Plus Environment
material (DMAC-TRZ)
of as
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blue dopant to compose of the emission layer for fabricating the TADF blue organic
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light emitting diode (BOLED). The device realizes highly efficient device with the
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performance parameters: maximum brightness (Bmax) 57586 cd/m2, maximum current
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efficiency (CEmax) 35.3 cd/A, maximum power efficiency (PEmax) 21.4 lm/W,
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maximum external quantum efficiency (EQEmax) 14.1% and CIE coordinates (0.18,
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0.42). This device has the best performance record among the reported
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solution-processed TADF BOLED, and has the low efficiency roll-off as such: at the
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brightness as 1000 and 5000 cd/m2, its CEs are close, being 35.1 and 30.1 cd/A,
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respectively. Further doping the red phosphor Ir(dpm)PQ2 (emission peak λmax=595
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nm) into the blue emission layer, we obtain the TADF-Phosphor hybrid white OLED
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(T-P hybrid WOLED) with the high performance: Bmax 43594 cd/m2, CEmax 28.8 cd/A,
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PEmax 18.1 lm/W, and CIE (0.38, 0.44). This Bmax 43594 cd/m2 is better than that of
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the vacuum -deposited WOLED with blue TADF emitter 10000 cd/m2. This is also the
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first report on T-P hybrid WOLED with solution-processed emitting layer.
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INTRODUCTION
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White organic light-emitting diode (WOLED) is expected to be used as next
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generation solid state lighting and large display applications, in which phosphorescent
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emitters are usually included for taking the advantage of harvesting triplet excitons in 2 ACS Paragon Plus Environment
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ACS Applied Materials & Interfaces
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addition to singlet excitons, making the maximum internal quantum efficiency
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(IQEmax) 100 % becomes possible and therefore leading to high device performance1-4.
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For example, Kido and coworkers2 used 2,6-bis(3(carbazol9yl)phenyl)pyridine
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(26DCzPPy) and tris(4-carbazoyl-9- ylphenyl) amine (TCTA) as the mixed-host and
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the blue phosphor fac-tris(mesityl-2-phenyl-1H- imidazole) iridium(III) [fac-Ir(mpim)]
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and red phosphor iridium(III) bis-(2-phenylquinoly- N,C2′) dipivaloyl-methane
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[Ir(dpm)PQ2] as the guests to fabricate phosphorescent WOLED (PHWOLED) with
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double emission layers by vacuum deposition method. They achieved the excellent
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device performance: at 1000 cd/m2, external quantum efficiency (EQE) 24.4 %,
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power efficiency (PE) 51.7 lm/W and Commission Internationale de L’Eclairage (CIE)
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color coordinates (0.38, 0.42).
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Recently, thermally activated delay fluorescence (TADF) emitters have been
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proposed by Adachi and coworkers5 as attractive alternative emitter materials which
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possess small energy gap between single and triplet states (∆EST
