Enhancement of out-coupling efficiency of flexible organic light-emitting diodes fabricated on an MLA-patterned parylene substrate

摘要

Flexible organic light-emitting diodes (OLEDs) have attracted a great attention in the lighting market because of their exciting advantage to be fabricated as a freely shaped illumination source with no design restrictions. However, flexible OLEDs are difficult to commercialize due to their low power efficiency compared to fluorescent or inorganic light-emitting diodes. Accordingly, effective optical extraction techniques are needed to address this issue. In this study, we report development of a flexible OLED device fabricated on a poly-paraxylylene (parylene) substrate patterned with a micro-lens array (MLA). Ultra-thin parylene films were successfully applied as flexible polymer substrates for foldable OLEDs with enhanced out-coupling efficiency. It was confirmed that MLA-patterned parylene substrates do not have any negative impacts on the electrical properties of the OLEDs. On the contrary, the flexible OLEDs fabricated on these substrates for light extraction exhibited the current efficiency enhanced by a factor of 1.23 compared to the reference OLED. Thus, we present a simple and low-cost OLED fabrication method to enhance the light extraction out of flexible OLEDs.