Study On Optical Absorption Properties Of One Dimensional Microstructures Based On Rigorous Coupled Wave Analysis

When the light passing through the interface between two dielectric medium with different refractive indexes, the reflection phenomenon will happen, and it will produce energy loss at the same time. If the reflection is enhanced, the photoelectric conversion efficiency of the optical elements will be reduced. Due to the excellent performance of reducing the reflection, the optical microstructures are used in the solar cells more and more widely. With the development of micro machining technology, optical microstructures have been able to carry out large-scale fabrication and manufacture. In this thesis, combining with the recent development of the technology of optical microstructures, one-dimensional and periodical optical microstructures are designed to reduce the light reflection and enhance the absorption.In this thesis, firstly, the optical properties of several one-dimensional periodic microstructures on the surface of solar cells are studied by the Matlab programming based on rigorous coupled wave analysis(RCWA). By simulating the absorption properties of structures, the correctness of the program is verified, and the optimized structure is put forward.Secondly, two kinds of quasi-periodical microstructures are designed, whose height of either the grating layer(Structure 1) or the air layer(Structure 2) arranged according to the Fibonacci sequence. In the case of TM polarization, the absorption of the two kinds of microstructures is calculated by the rigorous coupled wave analysis method. The effects of Fibonacci sequence, filling ratio and relative height ratio on the optical absorption of one-dimensional microstructures are discussed, and the optical absorption properties of the two structures are compared. Such a conclusion is got: the optical absorption performance of Structure 2 is better, and when the Fibonacci sequence is S3, filling ratio is f=0.5 and relative height H=0.4, the averaged absorption could reach the maximum of 92.89% within the wavelength region of 300-1100 nm.Finally, a layer of silicon nitride thin film whose refractive index is between the air and the silicon substrate is deposited on the surface of the previous two microstructure., and the effect of film thickness on the optical absorption of the two structures is discussed. Conclusions are as follows: only for the coating thickness of the factors discussed in, after being coated, the optical absorption performance of structure 2 is better, and when the Fibonacci sequence is S3, filling ratio is f=0.7 and relative height H=0.4, the averaged absorption could reach the maximum of 95.17% within the wavelength region of 300-1100 nm.The research of this paper provides a theoretical reference both for the design of the surface microstructures of solar cells and the further improvement of energy conversion efficiency.