FAST LBIC SCANNING OF SOLAR CELLS

摘要

For detection of local defects in solar cells LBIC (Light Beam Induced Current) is a widely used universal method. The resulting picture indicates differences in local series and shunt resistances and differences in local rate of minority carriers recombination. A laser beam scanning over the solar cell surface is routinely used in this test. This process may take several hours depending on demanded picture resolution. A method for fast scanning of solar cells based on the LBIC measurement was proposed and tested. Instead of laser beam a linear light source consistent of multiple SMD LED diodes is used. Scanning is performed in both X and Y axes. In principle one scan in each coordinate is sufficient. The resulting current response is influenced by all defects allocated in the actual position of the actuating light beam line. The picture of the solar cell defects is computed combining the contributions from each line in both X and Y axes. Result of this computation is not the same as the LBIC picture nevertheless it gives an information about the position and about the change of intensity of the local current. Data computation was made by MATLAB program. Using red, green and blue LEDs there is a possibility to obtain different depth of light absorption area. This way the faults in bulk so as near the surface of the solar cell can be detected.