Ultrahigh light extraction efficiency light emitting diodes by harnessing asymmetric obtuse angle microstructured surfaces

We report an ultrahigh light extraction efficiency (LEE) light emitting diodes (LEDs) by incorporating innovative asymmetric obtuse angle microstructured surfaces. The quantitative simulations show that the LEE can be as high as 90% with realistic parameters. The physical mechanisms that enable such an ultrahigh LEE are also analyzed. It is believed that the main reasons are (1) the increased interaction surface area and (2) the better randomization effect by replacing the symmetric structure with the asymmetric obtuse angle structure. We also show that the proposed asymmetric obtuse angle microstructured surfaces are manufacturable. Experimental results also verify that a higher light extraction can be achieved by harnessing the asymmetric obtuse angle microstructured surfaces. Such an ultrahigh LEE can significantly increase the overall light efficacy of solid state lighting sources (SSL) and expedite the deployments of SSL sources.