Defect detection of solar cells based on electroluminescence imaging

In order to detect the hidden defects of the solar cells, the eletroluminescence image was obtained by applying a certain forward bias voltage to solar cell in the darkroom using the light sensor CCD camera. The experiments were carried out at three states: without optical filter, filtering the wavelength less than 800 nm, and filtering the wavelength greater than 800 nm. It is found that the detection effect is the best only under the lens of filtration of less than 800 nm wavelength. It proves that the cell mainly emits infrared light of 850~1200 nm. By controlling the detecting time, it is found that the light intensity is varied with the detection time, and also varied with the forward bias voltage in the same detection time. This method can detect all kinds of hidden defect type of the solar cells. Under the reverse voltage , thin film cell appears small spots which show defect area and density, and the studies prove that thin film cell also can send infrared light and the defects exist in the cell. In detecting low power cell, it is found that there are serious defects in the cell. The results show that infrared detection has rapid and convenient intuitive features for solar cells defect detection.