Quantitative Defect Analysis on Solar Cells by Laser Beam Induced Current (LBIC) Measurements and 3D Network Simulations

Abstract

ABSTRACTMeasurements with the CELLO (solar cell local characterization) technique in the LBIC (laser beam induced current) mode under dark conditions with various constant bias voltages are used to analyze the lateral distribution, and mean values, of photocurrent response maps. Local solar cell defects such as local shunts were found to have a characteristic bias voltage dependence: At negative and small positive voltages a local shunt resistance gives less current response than the adjacent area. Upon applying higher positive voltages, a transition of the mean value to lower current response and an inversion of the local defect characteristics are found. These results were modeled by a newly introduced three dimensional (3D) equivalent circuit model of a solar cell divided into subcells.Measurements and simulations of solar cells with various local defects show our method to be a new powerful tool for the quantitative analysis of local solar cell defects.