Study On The Effect Of Complex Photonic Crystals On The Light Extraction Efficiency Of LED

Light-emitting diode(LED)is a device that can directly emit light by electro-optical conversion.It is called the fourth-generation illumination source and has the characteristics of energy saving,environmental protection,safety,small size,long life and low power consumption.However,the current LED light extraction efficiency(LEE)is still low,which seriously restricts the application and development of LED.Therefore,how to improve the light-emitting efficiency of LED has become a hot topic at home and abroad.In this paper,we mainly study the band gap characteristics of photonic crystals from photonic crystals,and then introduce complex-period photonic crystals to study complex-period photonic crystal LEDs.The LEE of GaN-based LED was improved by designing different complex-period photonic crystal structures.The effects of various structural parameters of complex-period photonic crystals on the LEE of LED are investigated.The main research contents are as follows:Firstly,the influence mechanism of photonic crystal periodicity and its lattice type on its optical band gap is studied.The band gap diagram corresponding to the radius of different dielectric columns is calculated by plane wave expansion method and the band gap width is calculated.The results show that the band gap width of the triangular-arranged single-cycle and complex-period photonic crystals is larger than that of the square-arranged photonic crystal.The band gap width of the complex-period photonic crystal is wider than that of the single-period photonic crystal because the complex periodic structure reduces the symmetry of the original single-period structure,but increases the photonic band gap.Secondly,the influence of the microstructure of complex-period photonic crystal on the LEE of LED is studied.The effects of semi-ellipsoidal and hemispherical micro-structured complex-period photonic crystals on the LEE of LED are studied.Studies have shown that hemispherical micro-structured complex periodic photonic crystals are more conducive to improving the LEE of LED than semi-ellipsoidal microstructures.Finally,the structural parameters of the hemispherical microstructure complex-period photonic crystal are optimized based on the finite difference time domain method,and the optimal LED LEE is obtained.Three materials of ZnO,GaN and SiC are simulated in hemispherical micro-structured complex periodic photonic crystals.The results show that the hemispherical micro-structured complex-period photonic crystals of GaN materials have better LEE than the other two materials.The LEE was maximum at 27.32% for a lattice constant of the complex structure of GaN material of 1.45 ?m,a radius hemisphere R of 0.6 ?m,and a radius of the small hemisphere r of 0.18 ?m.