Tenfold increase in efficiency from a reference blue OLED
Abstract Starting from a reference single-layer light-emitting diode based on the blue phosphorescent bis-cyclometallated iridium complex FIrpic as guest, hosted in a PVK (non-conjugated poly(vynilcarbazole)) matrix, different strategies are followed to improve the efficiency of the devices through the combination of solution processed and evaporated layers. Injection of charges from the electrodes has been varied by using different conductive PEDOT: PSS as hole injection layer and a nanoscale Cs2CO3 interlayer as electron injection and hole-blocking film. Furthermore, a separated electron injection/hole blocking evaporated layer, TPBi or 3TPYMB, is introduced in double-layer devices to enh…
Langmuir monolayers and Langmuir–Blodgett films of ferritin prepared by using a surfactant mixture of eicosylamine (EA) and methyl stearate (SME)
Abstract Magnetic Langmuir–Blodgett films of ferritin have been prepared by using the adsorption properties of a 1/4 mixed monolayer of eicosylamine (EA) and methyl stearate (SME). BAM images show that a more homogeneous distribution of ferritin at the air–water interface is achieved by using this mixture of surfactants instead of the DODA/SME mixed matrix of a previous work. Transfer of the monolayer onto different substrates allowed the preparation of multilayer LB films. Infrared and UV–Vis spectroscopies indicate that ferritin molecules are incorporated within the LB films. Furthermore, UV–Vis spectroscopy measurements reveal that the amount of ferritin incorporated into these LB film h…
Solution processable high band gap hosts based on carbazole functionalized cyclic phosphazene cores for application in organic light‐emitting diodes
A new class of solution processable dendrimers based on cyclic phosphazene (CP) cores have been prepared and used as host materials for blue and green organic light emitting diodes (OLEDs). The dendrimers are prepared in high yield from minimal step reactions, are soluble in common solvents for solution processing, are amorphous, and have excellent thermal properties necessary for application in OLEDs. OLED efficiencies of 10.3 cd/A (4.2 Im/W) and 35.3 cd/A (33.5 Im/W) were achieved using commercially available Flrpic and Ir(mppy) 3 as blue and green phosphorescent emitters, respectively. These efficiencies were 2x higher than control devices prepared using poly(N-vinylcarbazole), the most …
Combined thermal evaporated and solution processed organic light emitting diodes
Abstract Highly efficient, partly solution processed phosphorescent red, green and white organic light emitting diodes with small molecular weight host materials are prepared from commercially available starting compounds. Starting from an evaporated reference device, layers are stepwise replaced by solution processed layers. Replacing the evaporated hole transport layer by a solution processed polymer interlayer does not affect the performance and allows spincoating of the emissive layer after annealing of the polymer. Devices with, next to the spincoated hole injection and transport layer, a solution processed emission layer show similar characteristics and efficiencies as the reference d…
Segregation of lipid in Ir-dye/DMPA mixed monolayers as strategy to fabricate 2D supramolecular nanostructures at the air–water interface
A novel pseudospherical fluorinated iridium(III) derivative, Ir-dye/PF6, [Ir(F2-ppy)2(bpy)]PF6 (F2-ppy = 2-(2,4-difluoro)phenylpyridine, bpy = 2,2′-bipyridine), has been organized by using a lipid matrix, DMPA (dimyristoyl-phosphatidic acid), in several molar ratios at the air–water interface. The molecular organization of both components and the degree of miscibility in the different mixed films have been inferred by surface techniques such as π–A isotherms, ellipsometry, reflection spectroscopy, Brewster angle microscopy (BAM), and IR spectroscopy for the LB films, additionally the results have been discussed according to the additivity rule. The equimolecular Ir-dye/DMPA mixture leads to…
Soret emission from water-soluble porphyrin thin films: effect on the electroluminescence response
The emission properties of TSPP [tetrakis(4-sulfonatophenyl) porphyrin] and TMPyP [tetrakis(4-methylpyridyl) porphyrin] in thin films, prepared both by the Langmuir–Blodgett technique and the spin-coating method, have been investigated. Surprisingly, in most of the samples analyzed, the emission spectra do not show the usual two bands typical of porphyrins (in the region 650–750 nm), and depend strongly on the excitation energy. The origin of a new emission band detected at ∼480–500 nm is discussed in terms of the nature of the porphyrin aggregates. Moreover, we demonstrate that the presence or absence of this band in the fluorescence spectrum is directly related to the generation of electr…
Molecular organization of a water-insoluble iridium(III) complex in mixed monolayers.
Abstract In this work, organized mixed monolayers containing a cationic water-insoluble iridium(III) complex, Ir-dye, [Ir(ppy)2(tmphen)]PF6, (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline, and ppy = 2-phenylpyridine), and an anionic lipid matrix, DMPA, dimyristoyl-phosphatidic acid, with different molar proportions, were formed by the co-spreading method at the air–water interface. The presence of the dye at the interface, as well as the molecular organization of the mixed films, is deduced from surface techniques such as π – A isotherms, Brewster angle microscopy (BAM) and reflection spectroscopy. The results obtained remark the formation of an equimolar mixed film, Ir-dye/DMPA = 1:1. B…