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Emitters displaying thermally activated delayed fluorescence (TADF) can lead to highly efficient organic light-emitting diodes (OLEDs). Such emitters are usually incorporated into the emissive layer (EML) at a relatively low concentration (<20 wt. %) with respect to a host material, a guesthost approach inherited from conventional fluorescent or phosphorescent OLEDs. Here, detailed studies on OLEDs, in which the concentration of oBFCzTrz (a blue-emitter displaying TADF) in a DPEPO host was varied from 8 to 100 wt. %, reveals that oBFCzTrz displays ambipolar transport and limited fluorescence-quenching due to aggregation. For instance, a neat film of oBFCzTrz maintains a photoluminescence quantum yield of 82%. We demonstrate that OLEDs with an EML having an oBFCzTrz concentration of 50 wt. % in DPEPO yield a maximum external quantum effi- ciency (EQE) of 25.5% with an EQE roll-off of 10% in the range from 10 to 1000 cd/m2 and Commission Internationale de l'Eclairage color coordinates of (0.20, 0.44). OLEDs with smaller or larger oBFCzTrz concentrations display smaller maximum EQE values. OLEDs with a neat oBFCzTrz EML display a maximum EQE of 14.0%. Time-resolved electroluminescent decay studies, and analysis using a simple model, reveal significant differences in transport, trapping, and recombination in these devices. [ABSTRACT FROM AUTHOR]

Emitters displaying thermally activated delayed fluorescence (TADF) can lead to highly efficient organic light-emitting diodes (OLEDs). Such emitters are usually incorporated into the emissive layer (EML) at a relatively low concentration (<20 wt. %) with respect to a host material, a guest-host approach inherited from conventional fluorescent or phosphorescent OLEDs. Here, detailed studies on OLEDs, in which the concentration of oBFCzTrz (a blue-emitter displaying TADF) in a DPEPO host was varied from 8 to 100 wt. %, reveals that oBFCzTrz displays ambipolar transport and limited fluorescence-quenching due to aggregation. For instance, a neat film of oBFCzTrz maintains a photoluminescence quantum yield of 82%. We demonstrate that OLEDs with an EML having an oBFCzTrz concentration of 50 wt. % in DPEPO yield a maximum external quantum efficiency (EQE) of 25.5% with an EQE roll-off of 10% in the range from 10 to 1000 cd/m2 and Commission Internationale de l'Eclairage color coordinates of (0.20, 0.44). OLEDs with smaller or larger oBFCzTrz concentrations display smaller maximum EQE values. OLEDs with a neat oBFCzTrz EML display a maximum EQE of 14.0%. Time-resolved electroluminescent decay studies, and analysis using a simple model, reveal significant differences in transport, trapping, and recombination in these devices. [ABSTRACT FROM AUTHOR]

Stacked inverted top-emitting white electrophosphorescent organic light-emitting diodes (OLEDs) are demonstrated. The OLEDs consist of orange and blue light-emitting units interconnected with a connecting unit of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile/Al/LiF. These OLEDs combine the features of having inverted electrode positions, top-emission, and a stacked architecture. They exhibit an average current efficacy of 26.5 cd/A at a luminance of 100 cd/m2. Single-unit inverted top-emitting OLEDs based on the constituent orange and blue light-emitting units are also characterized for comparison. The current efficacies of the orange and blue OLEDs are 21.2 cd/A and 32.6 cd/A, respectively, at a luminance of 100 cd/m2. [ABSTRACT FROM AUTHOR]

Green electrophosphorescent organic light-emitting diodes (OLEDs) with inverted top-emitting structures are demonstrated on bio-compatible shape memory polymer (SMP) substrates for wearable electronic applications. The combination of the unique properties of SMP substrates with the light-emitting properties of OLEDs pave to the way for new applications, including conformable smart skin devices, minimally invasive biomedical devices, and flexible lighting/display technologies. In this work, SMPs were designed to exhibit a considerable drop in modulus when a thermal stimulus is applied, allowing the devices to bend and conform to new shapes when its glass transition temperature is reached. These SMP substrates were synthesized using 1,3,5-triallyl-1,3,5-triazine-2,4,6(1 H ,3 H ,5 H )-trione (TATATO), trimethylolpropane tris(3-mercaptopropionate) (TMTMP), and tricyclo[5.2.1.0 2,6 ]decanedimethanol diacrylate (TCMDA), and show a low glass transition temperature of 43 °C, as measured using dynamic mechanical analysis (DMA). The OLEDs fabricated on these substrates exhibit high performance with a maximum efficacy of 33 cd/A measured at a luminance of 1000 cd/m 2 , and a peak luminance of over 30,000 cd/m 2 . [ABSTRACT FROM AUTHOR]

Highlights: [•] Stacked inverted top-emitting green organic light-emitting diodes. [•] Devices are demonstrated on flexible glass substrates (Corning® Willow™ Glass). [•] A maximum current efficacy of 205cd/A at 103cd/m2 is achieved. [•] Double-unit OLED acts like two single-unit OLEDs electrically connected in series. [•] Interconnecting unit consists of thin layers of HAT-CN/Al/LiF. [ABSTRACT FROM AUTHOR]