Optimization of Photonic Crystal OLEDs via Electron Transport Layer Doping

Microcavity organic light emitting diodes (OLEDs) and metal dielectric photonic crystal OLEDs (MDPC) consisting of stacked microcavities offer unique ways to shape emission spectra into discrete, narrow-linewidth emission peaks. The use of identical silver-aluminum alloy electrodes (Ag:Al) for both anode and cathode appears to be one method of producing more clearly resolved peaks. However, using only Ag:Al alloy presents its own issues. While possessing ideal optical properties, the metal lacks the ability to inject both negative (electrons) and positive (holes) charges due to the work function mismatch. Efforts were made to replace one electrode with silver-magnesium alloy to mitigate this problem, but these devices lacked thermal stability. This project sought to use doping methods on the organic electron transport layer (ETL) of the OLED photonic crystal structure to increase charge injection, thereby enabling the use of matching Ag:Al electrodes. Doping of the organic ETL with Cs$_2$CO$_3$, in the 10 nm closest to the cathode successfully allowed electron injection, enabling the use of Ag:Al alloys for both anode and cathode in microcavity OLEDs and MDPC OLEDs with 2 and 3 unit cells.