Abstract
An efficient color-tunable hybrid white organic light-emitting diode is demonstrated with double interlayers of 2,7-bis(carbazol-9-yl)-9,9-ditoylfluo- rene/2-(diphenylphosphoryl) spiroflu-orene (DMFL-CBP/SPPO1) inserted between blue fluorescent and yellow phosphorescent-emitting layers, and exhibits Commission Internationale de l’Eclairage (CIE1931) ranging from warm white (0.4368, 0.4497) to cool white (0.2781, 0.2896) with driving current density from 0.2 to 40 mA/cm2. The recombination of singlet and the triplet excitons in blue fluores-cent-emitting layer and yellow phosphorescent-emitting layer, respectively, can be modulated by both the thickness of these double interlayers and the applied current densities.
Highlights
Since the first practical sandwiched organic light-emitting diode (OLED) was reported by C.W
After the 110 nm indium-tin-oxide (ITO) film coated glass substrate with a sheet resistance of 15 Ω/□ is treated by UV-ozone for 15 min, layers of molybdenum trioxide (MoO3),N,N’-di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine (NPB), 2-methyl-9,10-bis(naphthalen-2-yl)anthracene: 4,4’-bis(9-ethyl-3carbazovinylene)-1,1’-biphenyl (MADN: BCzVBi), DMFL-CBP/SPPO1, 2',2''(1,3,5-benzinetriyl)-Tris(1-phenyl-1-H-benzimidazole):Iridium(III)bis(4-phenyl thieno[3,2-c]pyridinato-N,C2')acetylacetonate (TPBi: PO-01), bathophenanthroline (Bphen), tris-8-hydroxyquinoline aluminium (Alq), lithium quinolate/ aluminum (Liq/Al), which are used as hole injecting layer, hole transporting layer, blue fluorescent emitting layer, double interlayers, yellow phosphorescent emitting layer, hole blocking layer, electon transporting layer, and bilayer cathode, respectively, are subsequently thermally evaporated under a base pressure of 2 × 10−6 Torr
Devices B (C) shows maximum current efficiency and power efficiency of 27 cd/A (24.5 cd/A) and 22.7 lm/W (20.1 lm/W), respectively. These are attributed to that the exciton generation interface should be located at the interface of DMFL-CBP/SPPO1 owing to the high lowest unoccupied molecular orbital (LUMO) of DMFL-CBP (−1.29 eV) and the low highest occupied molecular orbital (HOMO) of SPPO1 (−6.5 eV) which can block electrons and holes at this interface, respectively
Summary
Since the first practical sandwiched organic light-emitting diode (OLED) was reported by C.W. Hybrid white organic light-emitting diodes (HWOLEDs), which posses the advantage of both the long stability of the blue fluorescent-emitting layer based OLEDs and the high electroluminescent efficiency of yellow phosphorescent-emitting layer based OLEDs, have been considered as a potential light source for lighting and display [5]. Seldom double interlayers are reported in the HWOLEDs. In this work, double interlayers of 2,7-bis(carbazol-9-yl)-9,9-ditoylfluorene/2(diphenylphosphoryl) spirofluorene (DMFL-CBP/SPPO1) is inserted between the blue fluorescent emitting layer and yellow phosphorescent emitting layer to manipulate the exciton generating zone. An efficient HWOLED is realized with a large chrominance span from CIE (0.4368, 0.4497) to CIE (0.2781, 0.2896)
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