Characteristics Of Light Extraction For Surface Photonic Crystal Light Emitting Diode

Light emitting diode(LED),as a highly efficient and environmentally friendly green solid light source,are widely used in various fields,but the problem of low efficiency is also limited to its large-scale use.Therefore,the researchers have done a variety of research on this issue,but also achieved good results,which mainly to improve the use of photonic crystal LED light efficiency of the research results are more significant.However,most of the previous use of complete photonic crystals to improve the light-emitting diode light extraction efficiency,less use with microcavity photonic crystals.However,if the point defects are introduced into these perfect surface photonic crystals to form the surface photonic crystal microcavity,it is likely that the light extraction efficiency and spatial distribution of the LED are more significant due to the strong local effect of the surface microcavity on the light influences.Based on this paper,a kind of LED based on surface microcavity photonic crystal is proposed and studied.The beaming collimation effect is generated by the coherent coupling between the outgoing light of multiple resonators,so as to improve the efficiency of light extraction,The spatial directivity has also been improved.By optimizing the structure of the surface photonic crystal structure,the light extraction efficiency of the surface microcavity photonic crystal LED is improved by 77% compared with that of the complete photonic crystal LED,and the brightness of the normal slab LED is more than 1.8 times.At the same time,the micro-cavity photonic crystal LED has a more obvious far-field energy convergence effect than the ordinary LED and the complete photonic crystal LED,so that the outgoing light has better spatial directivity.In the process of proposing and studying this surface microcavity photonic crystal LED,the bandgap effect,photon local effect and grating diffraction effect of photonic crystal are mainly used.In order to design and optimize the structure of this efficient LED,the following conclusions are obtained by simulating the relationship between the forbidden band and photonic local characteristics of photonic crystals and its main structural parameters.With the increase of the lattice constant of the photonic crystal,the center of the bandgap frequency decreases,and the bandgap width decreases with a certain range.With the increase of the photon crystal duty cycle,the frequency of the bandgap center of the photonic crystal is gradually reduced,and the phenomenon of multi-banding occurs at the same time.When the duty ratio increases to a certain extent,it will show a narrow bandgap or even no Band gap effect.With the increase of the radius of the center of the microcavity defect,the center frequency of the microcavity gradually decreases,and the normalized power corresponding to the center frequency also decreases.The structure of this surface microcavity photonic crystal LED is designed and optimized by these laws,and the effect of light extraction is achieved.