Simulation Of Light Trapping Structure For Amorphous Silicon Solarcell And Parameter Estimation

The radiative properties are significantly different from the conventional radiation when the geometrical scale of the structure is comparable to the wavelength of thermal radiation, which can be employed to control the thermal radiatio n characteristics of the structures. As a typical periodic microstructure, gratings have a wide use range of applications such as solar cells, microelectronics cooling, thermal control of spacecraft. Based on the spectral selection properties on the surface of microstructure, the author designs two light trapping structures to improve the conversion efficiency of amorphous silicon thin film solar cell. The absorption of incident the increase significantly with the light trapping structures. At the same time, based on the spectral selection properties of the gratings, the grating parameters of different types are inversed. This is a new method for non-contact measurement. This thesis uses rigorous coupled wave analysis as forward problem method and standard particle swarm optimization as inverse problem method.Physical mechanisms of the special spectral selection properties are ascribed to surface plasmon polarizations, surface phonon polarizations and local magnetic polarizations. In the thesis the reason why gratings are wavelength-selective is explained with numerical results of RCWA. This research constructs the dispersion relation of SPPs at surface grating. Besides, the equivalent LC circuit model theory extends to the predications for the excitation conditions of local magnetic polarizations.In order to improve the conversion efficiency of amorphous silicon thin film solar cell, this thesis proposes a structure that is making grating structure between the ITO layer and the Si layer of amorphous silicon thin film cell to study the light trapping characteristics. As a result of local magnetic polarizations between the two layers, the absorption efficiency improve evidently in the near-infrared region. Based on the light trapping structure, this thesis also proposes a structure that is making grating structures at both the bottom and the top. In 0.73-0.83μm wavelength band, the absorption of the incident increases significantly because of the light trapping structure.At the same time, the grating parameters of different types are inversed based on the spectral selection properties of the gratings. Groove gratings, dual- groove gratings, thin film solar cells with rectangle gratings at bottom, thin film solar cells with rectangle gratings at both the bottom and top are inversed. The thesis analyses how the parameters affect the inversion results. Besides, the gratings are inversed according to the reflectance at different angles of incidence.