Sub-wavelength Grating Enhance Light Absorption In Thin-film Solar Cells

Sub-wavelength grating as a surface microstructure has important applications in both communication and green energy fields.The structural features of the subwavelength gratings could be classified into three categories: nano-periodic structure,random structure,as well as quasi-random structure.These diverse sub-wavelength gratings have their own advantages and disadvantages in thin-film solar cells of energy fields.The design of nano-periodic structure is simple,but it has narrow angle and bandwidth of light absorption.The random structure can solve the problem of narrow angle and bandwidth,but its absorption is low.The excellent performance of periodic and randon structure could be obtained by quasi-random structure,however there is no systematic method to design quasi-random gratings.As a result,the application of quasi-random structure grating is limited.To overcome this issue,the premise of quasirandon gratings is to devise periodic grating with excellent optical performance.Then a two-dimensional spiral grating is introduced on the surface of crystalline silicon solar cells to obtain both efficient and stable light absorption.In addition,a new method to design quasi-random grating is presented by random function and code.The work of this paper is mainly reflected in the following two aspects(1)A two-dimensional spiral grating is introduced on the surface of crystalline silicon solar cells to obtain both efficient and stable light absorption.By combining the spiral phyllotaxis of plants with the traditional simple subwavelength grating,the biomimetic 2D spiral grating is presented.Using the rigorous coupled wave analysis method,the absorption stability of the spiral grating solar cell is invested firstly.The absorption stability of grating mainly includes structural stability and angle stability.When the structure parameters are simultaneously deviated from the optimized structure by 15 percent,only a 4.84 percent decrease of the absorption is observed.For average polarizations,a small decrease of 17.86 percent from the maximum absorption is observed within an incident angle ranging from-70 to 70 degrees.In addition,the absorption efficiency of the spiral structure grating is studied.The integrated absorption of the optimal spiral grating cell is raised by about 73.89 percent compared with the conventional slab cell.The simulation results imply that the proposed spiral grating cells could indeed inherit the stability feature and high absorption efficiency of the spiral phyllotaxis.(2)A design method of quasi-periodic grating is put forward in this paper.Through analyzing the optical performance of order grating,random grating and quasi-random grating,and absorbing the advantages of those grating.A new method to design quasi-random grating is presented by random function and code.This new method makes the quasi-periodic grating structure can not only obtain the advantages of order grating in design and production,it also can obtain the advantages of disorder grating in optical performance,such as angle,bandwidth and polarization.