Coupling Efficiency Enhancement in Organic Light-Emitting Devices Using Microlens Array-Theory and Experiment

Microlens arrays are introduced on glass substrates to improve the out-coupling efficiency of organic light-emitting devices (OLEDs). The microlenses suppress waveguiding loss in the substrate. A theoretical model, based on electromagnetic wave propagation and geometric ray tracing, is developed to simulate the enhancement effects and optimize the structure parameters of the lens pattern. A simple soft-lithography approach is employed to fabricate the microlens array on glass substrates. With the use of an optimized lens pattern, an increase of over 85\% in the coupling efficiency of the OLED is expected theoretically. An increase of 70\% in the coupling efficiency is achieved experimentally, without detrimental effect to the electrical performance of the OLED.