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Deep Level Transient Spectroscopic Investigation of Carrier Trap Defects in p-Type mc-Si PERC Solar Cells After Elevated Temperature Light Soaking
C. Zhou, S. Zhou, F. Ji, W.J. Wenjing
Boron Doping, PERC Solar Cell, mc-Si, LeTID
Silicon Materials and Cells
Subtopic: Homojunction Solar Cells
Event: 36th European Photovoltaic Solar Energy Conference and Exhibition
Session: 2BO.1.2
147 - 150
ISBN: 3-936338-60-4
Paper DOI: 10.4229/EUPVSEC20192019-2BO.1.2
0,00 EUR
Document(s): paper


In boron-doped multi-crystalline PERC solar cells carrier traps were investigated by deep level transient spectroscopy after so-called “elevated temperature light –induced degradation” (LeTID). LeTID was carried out in Boron dopped mc-Si PERC solar cells for 30 hours. The current- deep level transient spectroscopy (I-DLTS) signals were detected from the full structure of the solar cells. I-DLTS-spectra allow measuring the deep energy levels parameters in large area of the p-n-junction solar cells with high leakage current and relatively large electrical capacitance. Comparing with the as-prepared PERC solar cell, DLTS signal increases in degraded cells which mean the defect concentration rise after light soaking at 70 oC for 30 hours. The apparent trap in an as-prepared and degraded PERC solar cells was related to Fe, with deep energy levels at about Ev + 0.485eV (Fei complex), and Ev + 0.295 eV (Fe-H), and their carrier capture cross-sections in the range of 10-14 – 10-16 cm2. The Fei complex peak with the maximum intensity indicates that it is hardly removed by means of phosphorus diusion gettering and hydrogenation process during PERC solar cell manufacture process. After LeTID, However, it is clear that even though the defect types are similar with those in the asprepared, their percentage changes in the LeTID solar cell. The Fe-H defect increase evidently and becomes the major defect withthe highest concentration after LeTID, which have higher concentration near surface. While Fei concentration decrease from the deep Si bulk to near silicon surface after LeTID. This imply that the Fei may bond with other impurity to form complex, or the nature of Fe defects changes in Si bulk during elevated temperature light soaking. It should be noted that we still can not exclude other transition metal ’s contribution because of their activation energy overlapping with Fe relative defect.