Diagnosis Of Solar Cell Defect Type Via Electroluminescence Imaging And Distributed Circuit Modeling

Vigorously developing the renewable energy which dominated by solar energy is an effective measure to solve the energy crisis,cope with the climate change and protect the ecological environment,and it is also an inevitable choice for human beings to seek the sustainable development.Solar cells can directly convert solar radiation energy into electricity,the breakthrough and improvement of conversion efficiency play a positive role in promoting the development and utilization of solar energy.However,the defects caused by the inherently granular structure of the material and specific procedures adopted for manufacturing will reduce the conversion efficiency of the solar cell and cause the overall performance degradation.In order to provide more valuable reference for the design and fabrication of solar cells,it is necessary to conduct thorough research on the defects.Absolute electroluminescence(EL)imaging can demonstrate the local defects and spatial nonuniformity of solar cells.Two-dimensional(2-D)distributed equivalent circuit modeling can be helpful for the in-depth understanding of electrical performance of solar cells.The combination of them provides a new approach to the research of the defects.In this thesis,the absolute EL images of Si,GaAs and CIGS solar cells with various injection current densities were measured.The simulations of the 2-D distributed equivalent circuit model of solar cells were performed by HSPICE.The different injection-current-dependent EL intensities of the dark spot defects and bright spot defects were studied.The origins of these defects were attributed to different defect types from an electrical viewpoint.Based on the absolute EL imaging with the 2-D distributed equivalent circuit modeling,a non-destructive and visual method for the quantitative diagnosis of the defects in solar cells was proposed.The main research contents of this thesis are as follows:(1)The J-V relations and absolute EL images with various injection current densities of Si,GaAs and CIGS solar cells were measured.With the simplified structure of the solar cell,the 2-D distributed equivalent circuit model was established,and the model parameters were extracted from the dark J-V curve.(2)The equivalent circuit model of solar cells was input into HSPICE for simulation by compiling the circuit netlist,and the subsequent data extraction and processing were carried out by writing scripts in MATLAB.The satisfactory agreement between experiments and simulations verified the feasibility and accuracy of the proposed 2-D distributed equivalent circuit model of solar cells.(3)The defects in Si,GaAs and CIGS solar cells were quantitatively analyzed: the dark spot defects in the Si and CIGS solar cells were attributed to the reduction of shunt resistance;the dark spot defects in the GaAs solar cell were attributed to the increase of series resistance;the bright spot defects in the CIGS solar cell were attributed to the reduction of series resistance.According to the different injection-current-dependent EL intensities of the defects,a method for identifying the defect types of solar cells was proposed.