Harm van Eersel, TUE

Title: Efficiency limiting processes in organic light-emitting diodes: effect of long-range excitonic interactions
Session: Tuesday 6 October, 14:45


Organic light-emitting diodes (OLEDs) are expected to complement conventional LEDs as large-area and ultrathin light sources. In terms of efficiency, however, OLEDs are not on par with conventional LEDs. One of the challenges is the drop of efficiency at higher luminance levels: roll-off. Various causes have been proposed, including triplet-triplet annihilation (TTA) and triplet-polaron quenching (TPQ). The relative roles and distance dependences of these processes are, however, a matter of debate. To settle this, we have developed a 3D Monte Carlo OLED device model. We have studied an idealized but realizable OLED stack, based on an active layer with the green phosphorescent dye Ir(ppy)3 embedded in various matrices, and find (1) that the energy levels of the matrix can have a significant effect on the roll-off, (2) that this effect is due to a change in the distribution of carriers and excitons in the device, and (3) that the sign and magnitude of this effect depends strongly on the TPQ range, but less on the TTA range.





 to be announced


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