A Study On The Noise Characterization Of Defects In Solar Cells

With the universal application of photovoltaic power generation,people have also put forward higher requirements for the reliability of solar cells.At present,the most widely used test methods to study the reliability of solar cells are electrical I-V testing,electroluminescence,and in-situ detection.Among them,it is difficult to accurately characterize the types and locations of the internal defect states of the cell by using the seven parameters extracted from the I-V characteristics;the electroluminescence cannot accurately divide the three stages of reverse breakdown of the cell;and the application of the in-situ detection method is often required.Samples are specially prepared for the sample and the packaged device cannot be directly detected.In view of the limitations of the above detection methods,the noise detection method is proposed,which is highly sensitive and nondestructive to defects in the semiconductor material and can be directly used to detect packaged devices.In view of these three advantages,based on the characterization of electrical parameters,this paper uses noise detection methods to conduct in-depth research on the defects in solar cells.The characteristics of the defects such as type,location,and size give the characterization results.Improvements in cell production process provide useful guidance.The paper selects two types of silicon solar cells—N+P monocrystalline silicon and PIN amorphous silicon solar cells.First,their energy band structures,failure modes,and initial noise test results are studied.Then corresponding designs are made.Stress aging experiments and finally give characterization results analysis.The specific work is as follows:(1)Amorphous silicon cells were subjected to light-induced attenuation experiments.By optimizing the electrical parameters characterization method,the dark saturated current value in the cell with the change of light duration was extracted,and it was found that the dark saturation current in the depletion zone increases with the duration of light.The increase reflects the increase of deep level defect concentration in the cell.Therefore,it is clear that the silicon dangling bonds in the depletion region play a major role in the light-induced attenuation of the amorphous silicon cell as a deep level recombination center.(2)For monocrystalline silicon solar cells,according to the irradiation damage mode and damage mechanism,the experiment of irradiation with γ-rays at different irradiation doses was designed,and the variation of electrical parameters and noise parameters of the cell with the cumulative dose of irradiation was compared.The main effect of cell radiation damage was the conclusion of displacement damage.(3)According to the initial noise test results of amorphous silicon solar cells,a GR noise characterization experiment was designed to compare the difference between the initial noise performance of GR noise and 1/f noise cell volt-ampere characteristics,and the corner frequency and cell bias based on GR noise.Based on the relationship between pressure and temperature,a variable pressure noise test experiment and a variable temperature noise test experiment were designed.Based on the sensitivity of the corner frequency to the bias voltage and the corresponding relationship between the corner frequency and the temperature,the deep energy level defects in the cell were found to be intrinsic.The layer and impurity levels correspond to copper impurities.(4)Using the reverse I-V detection,reverse C-V detection and reverse bias microplasma noise testing,a new cell reverse breakdown characteristics characterization method is presented,which accurately divides the three phases of reverse breakdown of the cell,while using the time series results of the microplasma noise,the width of the cluster defect that caused the reverse breakdown of the cell was calculated.