Controlling the optical efficiency of the transparent organic light-emitting diode using capping layers

The performance of transparent organic light-emitting diodes (TOLEDs) that use a combination of organic and inorganic capping layers (CLs) is reported. The first organic layer on top of the transparent cathode was used to increase the light output of the normally directed emission toward the top direction. The second layer, which had high-refractive-index inorganic materials on top of the first organic layer, was used as a reflector to enhance the efficiency of the bottom direction by taking advantage of the discrepancy in the refractive index against the air. By incorporating these CLs, control of the optical properties of the TOLEDs was achieved to allow the application of the transparent lighting-source.