Development of a Highly Efficient Hybrid White Organic-Light-Emitting Diode with a Single Emission Layer by Solution Processing

• Published in: ACS applied materials & interfaces 2018-02, Vol.10 (5), p.4851-4859
• Main Authors: Wu, Jun-Yi, Chen, Show-An
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.7b14695

We use a mixed host, 2,6-bis­[3-(carbazol-9-yl)­phenyl]­pyridine blended with 20 wt % tris­(4-carbazoyl-9-ylphenyl)­amine, to lower the hole-injection barrier, along with the bipolar and high-photoluminescence-quantum-yield (Φp= 84%), blue thermally activated delay fluorescence (TADF) material of 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine (DMAC-TRZ) as a blue dopant to compose the emission layer for the fabrication of a TADF blue organic-light-emitting diode (BOLED). The device is highly efficient with the following performance parameters: maximum brightness (B max) = 57586 cd/m2, maximum current efficiency (CEmax) = 35.3 cd/A, maximum power efficiency (PEmax) = 21.4 lm/W, maximum external quantum efficiency (EQEmax) = 14.1%, and CIE coordinates (0.18, 0.42). This device has the best performance recorded among the reported solution-processed TADF BOLEDs and has a low efficiency roll-off: at brightness values of 1000 and 5000 cd/m2, its CEs are close, being 35.1 and 30.1 cd/A, respectively. Upon further doping of the red phosphor Ir­(dpm)­PQ2 (emission peak λmax = 595 nm) into the blue emission layer, we obtained a TADF–phosphor hybrid white organic-light-emitting diode (T–P hybrid WOLED) with high performance: B max = 43594 cd/m2, CEmax = 28.8 cd/A, PEmax = 18.1 lm/W, and CIE coordinates (0.38, 0.44). This B max = 43594 cd/m2 is better than that of the vacuum-deposited WOLED with a blue TADF emitter, 10000 cd/m2. This is also the first report on a T–P hybrid WOLED with a solution-processed emitting layer.