Optical design of 200‐lm/W phosphorescent green light emitting devices based on the high refractive index substrate

Light extraction efficiency has been successfully enhanced by using high refractive index substrate coupled with micro‐lens array and weak micro‐cavity structure. Optical energy intensity including waveguide, substrate and external modes was analyzed based on wave optics. It was shown that most of the waveguide mode is turned to the substrate mode by the effect of high index refraction substrate. About a half of the light can be extracted from the substrate by the assistance of surface textured structure. An external quantum efficiency of 57% and a power efficiency of over 200‐lm/W were obtained in a green phosphorescent device. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)