A Study On Failure Mechanism And Its Characterization Methods Of Silicon Solar Cells In High And Low Alternating Stress

With the rapid development of human society, there is an urgent need of new resources to replace fossil fuel, such as solar, biomass, wind energy, ocean energy, hydropower, etc. Most of these energy sources are from solar energy since its feature of inexhaustible, no pollution and eternal use. That is the reason of its significant position in new resources.There are three major forms of using solar: photo-chemical conversion, photo-thermal conversion, and photovoltaic conversion, and the photovoltaic conversion is achieved via solar cells. At the present stage, the research on solar cells has two parts, one is to improve the conversion efficiency of solar cells and reduce its cost, and the other one is to study the quality of solar cells and analysis of its reliability, in order to improve the sensitivity and accuracy of reliability characterization methods. We mainly concentrate on the reliability analysis of the solar cell.Currently, there are many ways to characterize the reliability of solar cells, such as measuring the I-V characteristics of the solar cell to extract some electrical parameters; directly examining the defect of the solar cells via optical microscope and scanning electron microscope; researching reverse breakdown characteristics of the solar cells through the electroluminescent, etc. However, when it comes to the defect of the solar cell material and structure, these methods are less sensitive and more complicated. And the results are quite different when using different methods for extracting the parameters.The noise, as a tool for assessing solar cell quality and reliability, its validity and sensitivity have been confirmed extensively. And because of its non-destructive, noise is taken into account by increasing researchers. Via analyzing the defects inside the solar cells and noise led by them, much more reliability information in the solar cells will be achieved.This paper summarizes the electric properties and the noise properties of the solar cells. Based on analyzing failure modes and failure mechanisms in high and low temperature alternating stress of silicon solar cells, the experiment schedule is established, including the selection of the samples, the selection of high and low temperature alternating stress, and the description of the experiment programme, while the noise test method is proposed based upon the existing equipment in our laboratory. Through the analysis of experimental results, the validity and sensitivity of the noise test are indicated. The relationship of noise in solar cells and some parameters are obtained as well, i.e. positive relation with its life, negative relation with its efficiency, negative relation with its change rate of series resistance, and positive relation with its change rate of shunt resistance. Finally, solar cell 1/f noise of the unified model is established based on 1/f noise model of the number fluctuation of carriers and the mobility fluctuation, and the results are analyzed theoretically.