Spontaneous migration of additives to form interlayers in OLED

David Wang Auditorium, 3rd floor Dalia Maydan Bldg.
Liza Nuzman, MSc candidate

Liza Nuzman, MSc candidate
Department of Materials Science and Engineering Technion, Israel Institute of Technology, Haifa, 32000 ISRAEL
Organic light-emitting diodes (OLEDs) have potential advantageous qualities unavailable to inorganic devices, such as mechanical flexibility and solution processability. For efficient OLED devices it is necessary to increase charge injection efficiency, which is determined, for electron injection, by the energy barrier between the lowest unoccupied molecular orbital (LUMO) of the polymer and the cathode work-function. Hence, low work function metals are commonly used for cathodes. However, they are highly sensitive to environmental degradation, end to create detrimental quenching sites near the organic/cathode interface, and affect the long-term stability of devices by diffusion of mobile metal ions into the organic film. The presence of interlayers at the organic/cathode interface is known to modify the metal work function effectively enhancing charge injection and performance, and increasing device stability. In this work, we study the migration of additives from the organic film to the organic/metal interface during cathode deposition to spontaneously form an interlayer in OLED devices. We study the effect of additive concentration and thermal treatments on the interlayer formation and on the device performance. We show that the selfgenerated interlayers reduce device turn on voltage and enhance OLED device performance.

Supervisor: Prof. Gitti Frey.