High-quality all-fluorescent white organic light-emitting diodes obtained by balancing carriers with hole limit layer

• Published in: Optical materials Vol. 123; p. 111917
• Main Authors: Chen, Kai, Wu, Ruixia, Li, Xiaokang, Liu, Weiqiang, Wei, Zhipeng, Wang, Jiahai, Zhou, Liang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2022
• Subjects: Fluorescent emitter; Hole limit layer; Luminescent efficiency; White organic light-emitting diodes; Luminescent efficiency; Fluorescent emitter; Hole limit layer; White organic light-emitting diodes
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2021.111917

Broad-spectrum white organic light-emitting diodes (WOLEDs) based on all-fluorescent materials with excellent color stability were realized by precisely optimizing the doping concentrations of guests and the thickness of each functional layer. High-efficiency blue fluorescent emissive material 9,10-bis[4-(6-methylbenzothiazol-2-yl)phenyl]anthracene (DBzA) was selected as blue emitter and doped into first light emitting layer (EML), while red-emitting dopant 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidn-4-yl-vinyl)- 4H-pyran (DCJTB) was doped into green-emitting host material tris(8-hydroxyquinoline) aluminum (Alq3) as the second EML. Thin hole limit layer (HLL) was inserted to balance carriers' distribution within the two EMLs and to modulate the luminous intensity ratio of different emissions. Finally, the optimal WOLED exhibited the maximum current efficiency of 9.34 cd/A, power efficiency of 10.06 lm/W, brightness up to 29,364 cd/m2 and turn-on voltage of only 2.7 V. In addition, this device displayed stable Commission International de I'Eclairage coordinates from (0.339, 0.382) to (0.324, 0.354) with increasing current density. The highest color rendering index and corresponding correlated color temperature reach 85 and 5492 K, respectively, and the T50 lifetime reaches 7912 h. The achievement of these results fully exhibits the effectiveness of the HLL in improving spectral stability and operation lifetime. Broad-spectrum white organic light-emitting diodes based on all-fluorescent materials with excellent spectrum stability were fabricated by inserting hole limit layer between DBzA-doped TcTa blue emitting and DCJTB-doped Alq3 red emitting layers. [Display omitted] •Broad-spectrum all-fluorescent white organic light-emitting diodes have been obtained.•Hole limit layer was inserted to balance carriers' distribution within the two light emitting layers.•Well-matched energy levels of used materials help to balance carriers’ distribution.•Color-stabilized white organic light-emitting diodes with high color rendering index of 85 were obtained.