Surface Modulation Grating Design And Performance Optimization In Ultrathin Crystalline Solar Cells

For a long time,the shortage of energy and the resulting environmental pollution have become focus that be concerned by many countries.At present,with the increasing demand of the energy in the worldwide,conventional energy sources such as fossil fuels will be depleted in the next century,finding ways of cost efficient,environmentally friendly and sustainable energy generation as well as energy consumption,is one of our biggest challenges.It is necessary to develop and adopt alternative energy sources,especially long-term natural energy—solar energy.Solar cell is considered to be the main candidates that takes energy from the sun.However,the industrialization process of solar cell is restricted by cost and photoelectric conversion efficiency and other factors.In recent years,to construction of advanced silicon solar cell micro-structure have driven the recovery of solar cell industry,and reducing the cost of mass production stimulated the interest of researchers.Improving the photoelectric conversion efficiency in solar cells is the key to increase the absorption capacity of the device to the photon.At the same time,reducing the thickness of the device material can improve the economic efficiency of solar cells.Based on this point of view,the optical design of thin-film solar cells is the main research content,and the surface microstructure of grating solar cells with diffractive and light trapping characteristics were designed using the Rigorous Coupled-wave theory(RCWA),prolonging the optical propagation path of the light inside the solar cell and improving the optical absorption efficiency and photocurrent density of the solar cell.The main contents of this paper are:First of all,we designed three different composite grating models on the top surface of crystalline silicon solar cells and the structural parameters were optimized in the visible and near-infrared spectral regions using RCWA.The spectral response and the photocurrent density of the upper surface composite modulated grating are calculated.Numerical results and theoretical analysis show that the upper surface composite modulation grating structure has better light trapping ability than traditional grating.Especially,it is close to ideal light trapping ability in short wavelength band,which is of great significance to enhance light absorption and photocurrent.Secondly,the pyramid back grating is designed on the basis of the optimized upper surface composite grating.By optimizing the back gating parameters,the optical absorption curve and photocurrent density of the grating are very close to Yablonovitch limit when the equivalent thickness is 2?m,and generating an ideal photocurrent density is up to 34.6mA /cm~2.These results indicate that modulated grating structure is an important mean to improve the performance of thin-film solar cells.