Research On Absorption Properties Of Micro-Nano Resonant Gratings

In view of the advantages of its simple structure,low energy consumption,and ease of integration,micro-nano gratings are playing an increasingly important role in the realization of richly functional and large-scale integrated photoelectric circuits aspects such as detection,coupling,slow light,solar cells,and absorption.This paper mainly focuses on the trapped light and absorption effects of micro-nano gratings.Specifically,the rigorous coupled-wave analysis method and the time-domain finite difference algorithm are used in this paper to discuss the increasing trapped light effect of micro-nano grating structures on solar thin-film cells under solar incident conditions.And from the dynamic light field distribution diagram,the micro-nano gratings for the mechanism of enhanced photoelectric conversion performance of solar cells was analyzed.On this basis,the coherent absorption characteristics of micro-nano gratings tending to the absorption limit were studied.The paper mainly carried out work on the following aspects:First,a broadband micro-nano multi-tooth grating anti-reflection device was designed on the upper surface of the silicon active layer of solar thin-film solar cells.Theoretical analysis shows that the device can maintain reflectivity of about 3.43%in a wide range from 300nm to 1200 nm,which can better achieve the effect of anti-reflection.In order to make effective use of solar light passing through the upper anti-reflection grating,a two-dimensional multi-grating grating mirror was designed on the lower surface of the silicon active layer of solar thin-film solar cells,which can effectively transmit sunlight,extend the propagation path of the sunlight in the active layer,and then improve the photoelectric conversion efficiency.Theoretical analysis shows that in the waveband range from 300nm to 1300 nm,the device has an average reflectivity of more than 83.78%at incident angle of-85oto 85o.To fully play the role of the upper and lower double-layer gratings,the two structures of upper and lower the active silicon layer of the solar cells are introduced.Under the joint action of the double-layer grating,the average transmissivity of the solar cells is 0.262%,and the average reflectivity is 19.425%,and silicon active layer for the sunlight absorption rate can reach 80.31%,and the short-circuit current is40.88mA/cm~2.Finally,the paper analyzes the coherent absorption characteristics of the dielectric grating devices:when the two beams of light are incident coherently,the grating device can perform perfect coherent absorption of the incident light,while when the incident light is in opposite phase,the grating device can perform full reflection and transmission for incident light,and absorption efficiency is almost close to zero.