Effect Of Nanomorphology On Light Extraction Efficiency Of Light Emitting Diodes

As one of the important parts of energy conservation and environmental protection,the lighting industry has been strongly supported by the national policy.However,in order to achieve the goal of energy conservation,the performance of LEDs still needs to be further improved.For the problem of low light extraction efficiency of LEDs,besides hexagonal lattice and square lattice,the ladybug lattice and archimedes A7 lattice were designed on the surface of blue LEDs to study the effect on improving light extraction efficiency.The transmission angular spectra of diffraction orders with different periodic nanostructures are analyzed.It is found that the competition of different diffraction orders of light by nanostructures is one of the important factors affecting the light extraction efficiency.In addition,due to the different luminescence characteristics of deep UV LEDs and blue LEDs,a double-layer nanostructure is proposed to effectively enhance the extraction efficiency of TE and TM mode light,so as to improve the luminous efficiency of deep UV LED,The main research contents are as follows:(1)We have studied the effect of ITO surface nanotopography on the light extraction efficiency of blue LEDs,and we found that the period parameter and the ratio of radius to period(r/p)had a great influence on the enhancement of light extraction efficiency of LED.After parameter optimization,the light extraction efficiency is enhanced by about 80%.To investigate the physical mechanism of nanotopography enhancing the light extraction efficiency of LEDs,the transmission angular spectra of different nanotopography were simulated.The transmission angular spectra demonstrated that the improvement of light extraction was achieved by the competition among the different diffraction mechanisms.In order to study the influence of production deviation on light extraction efficiency,radius error and position error are added to the optimized A7 lattice structure.And the influence of random parameters on light extraction efficiency was studied when the random parameters varied in the range of 20 nm to 100 nm.The effect of small range random error on the light extraction efficiency is not obvious,and with the increase of the random range,the light extraction efficiency will decrease significantly.(2)We have studied the effect of surface nanostructures and embedded nanostructures on light extraction efficiency of UV LED.By optimizing the period and the ratio of radius to period(r/p)of the nanostructures,we have obtained the optimal nanostructures.And then we found that the surface nanostructures are more conducive to the extraction of TM mode light,which is about 14 times enhancement compared with the TM mode of planar LEDs.However,the embedded nanostructures are more conducive to the extraction of TE mode light,which is about1.5 times enhanced compared to the TE mode of the planar LEDs.Then,combining the advantages of the two structures,a double-layer photonic crystal structure is proposed,and the total light extraction efficiency is enhanced by about 2.45 times compared with the planar structure.The proposed A7 lattice structure can be used to design high-efficiency blue led devices,which provides a theoretical guidance for the production.The double-layer nanostructure deep ultraviolet led model provides a design basis for the experimental preparation of highperformance deep ultraviolet led devices,and is expected to become a new type of nanostructure deep ultraviolet led.