Chemical structures of key materials used in harvesting OLEDs. See Table I for HOMO, LUMO, and triplet energy levels.
Photoluminescence spectra of frozen solutions at 77 K. (a) MQAB, prompt emission (mixed fluorescence and phosphorescence, dotted curve), and delayed phosphorescence (solid curve), showing a singlet-triplet splitting of about 0.3 eV. (b) Phosphorescence of CBP and MQAB, showing that the triplet energy of MQAB is about 0.06 eV less than that of CBP. Arrows indicate the points identified with the excitation energies. Solvent is 1:2:2 mixture of iodobenzene:dichlorobenzene:toluene.
EQE as a function of the MQAB concentration and current density for conventional devices: MQAB . Inset: Spectra of devices with and without MQAB in the LEL.
Structure of the harvesting OLED. Dopants are described in italics.
Spectra of harvesting hybrid and blue fluorescent OLEDs. The blue device has the same structure as (Fig. 4) except that the yellow phosphorescent emitter is omitted. The blue device without TCTA has the layer structure of MQAB . The data were taken at .
EQE as a function of current density shown for the total EQE and for the blue and yellow portions of the EL spectrum of the harvesting device.
Time-resolved EL of the device showing the time evolution of prompt blue, delayed yellow, and total emissions. Inset: Delay between time-resolved maxima of blue and yellow emissions as a function of SL thickness. For device structure see Fig. 4. The device was excited by electrical pulse for , on state, and −10 V off state.
Magnetic field effect on the blue and yellow spectral components of a harvesting device. Emissions are separated by long pass (, trace a) and band pass (460 nm, trace b) filters. Trace c shows the magnetic field behavior of the EL of a conventional yellow triplet device of the structure .
EDEPR spectra of OLED devices of the structure , where x% is 0%, 10%, and 20%. The dotted curve is a triplet reference spectrum of .
Effect of SL thickness on EQE of blue and yellow components of the spectrum. Layer structure: MQAB . The data were taken at .
EQE as a function of BNA doping of the TCTA layer in a device shown for the total emission and for blue and yellow components of the EL spectrum. Organic layer structure: NPB BNA MQAB (37 nm). The data were taken at .
EQE as a function of current density shown for the total EQE and for the blue and red components of the EL spectrum of a harvesting device.
Time-resolved EL of a device showing time evolution of blue and red components and total emission. Layer structure: MQAB .
EL spectra of OLEDs. Layer structure: MQAB or x% PMB . The data were taken at .
EDEPR spectra of devices of the structure . Trace a: no dopant, trace b: , trace c: , and trace d: and . The dopant concentrations were 5% for PMB and 1% for MQAB.
Spectra of harvesting hybrid and BF OLEDs. The blue device has the same structure as except that the green phosphorescent emitter is omitted and the device has the structure MQAB . The data were taken at .
Spectra of white harvesting devices with different red triplet emitters. The data were taken at .
Molecular properties. Columns 2 and 3: HOMO and LUMO energies derived from electrochemistry. Columns 4 and 5: Triplet energies evaluated from phosphorescence spectra and DFT computations. Electrochemical processes are reversible unless otherwise noted.
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