In the use of crystalline silicon solar cells, the micro defects, such as cracks, the grain boundary dislocation, broken
metal grid fingers, etc., will seriously affect the efficiency and the life of crystalline silicon solar cells. Therefore, it is
necessary to detect the micro defects of Si solar cells rapidly and accurately in the production process. In this paper,
firstly, the relationship between the electroluminescence (EL) intensity from Si solar cells under the forward bias and
minority carrier diffusion length is simulated based on the calculation under the condition of ideal P-N junction model.
There exists one to one quantitative agreement. We find that the relationship referred above is nonlinear. Secondly, the
relationship between the defects in Si solar cells and minority carrier diffusion length (EL intensity) is summed up. The
defects and minority carrier lifetime are also in accord with this relationship. Based upon these, the micro defects in Si
solar cells could be made out in theory. With experiments, the defects in c-Si solar cells and poly-Si solar cells are
detected clearly from EI images. Theory analysis and experiments show that the method is reasonable and efficient.