Comparison of LID and Electrical Injection Regeneration of PERC and Al-BSF Solar Cells from a Cz-Si Ingot

Abstract

In order to study the effect of device structures and silicon wafer positions on light-induced degradation (LID) and regeneration, five groups of industrial PERC and Al-BSF solar cells were fabricated by using silicon wafers from different positions of a B-doped Czochralski silicon (Cz-Si) ingot. Then, the cells were subjected to a dark annealing (200 °C, 30 min), the first LID (45 °C, 1 sun, 12 h), an electrical injection regeneration (175 °C, 18 A, 30 min) and the second LID (45 °C, 1 sun, 12 h) in order, and the variations of performance of the cells with processing time were measured. It was found that after the electrical injection regeneration, the efficiency losses of PERC cells decreased from 1.28–1.76%absolute in the first LID to 0.09–0.16%absolute in the second LID, while those of Al-BSF cells decreased from 0.3–0.66%absolute in the first LID to 0 in the second LID. The efficiency losses of PERC cells during the first LID were caused by the co-action of B-O-defect-induced LID (BO-LID) and dissociation of Fe-B pairs, and the latter contributed 5.81–9.56% of the efficiency loss, while those of Al-BSF cells during the first LID were almost contributed by BO-LID solely. For both kinds of cells, the cells made from the silicon wafers from middle of the ingot had the best performance throughout the experiment. In addition, the LID and regeneration treatments only affected the spectral response of the cells in the wavelength larger than 700 nm.

Keywords

• light-induced degradation (LID)
• boron–oxygen defects
• iron–boron pairs
• regeneration
• Czochralski silicon
• passivated emitter and rear cell (PERC)