We investigate a set of transparent organic LEDs (TOLEDs) with different organic capping layer (OC) thicknesses to understand the capping layer effect. We find that thickness variation of the OC strongly influences the emission properties of TOLEDs and exhibits different trends for top or bottom emission. The external quantum efficiency for the top side can be enhanced by a factor of 63%, but that of the bottom side only by 4% compared to a reference device without an OC. Additionally, we demonstrate that the introduction of the OC is an effective method to control the bottom-to-top emission ratio within a measured range from 2.87 to 6.05.
© 2011 Optical Society of America
Original Manuscript: February 8, 2011
Revised Manuscript: March 21, 2011
Manuscript Accepted: March 21, 2011
Published: April 13, 2011
Jonghee Lee, Simone Hofmann, Mauro Furno, Michael Thomschke, Yong Hyun Kim, Björn Lüssem, and Karl Leo, "Influence of organic capping layers on the performance of transparent organic light-emitting diodes," Opt. Lett. 36, 1443-1445 (2011)