Title:	Kinetics of the Degradation and Regeneration of p-Type Multicrystalline Silicon under Dark Anneal
Author(s):	C. Vargas Castrillon, G. Coletti, D. Payne, C. Chan, Z. Hameiri
Keywords:	Annealing, Degradation, Hydrogen, Multicrystalline Silicon, Dark
Topic:	Silicon Cells
Subtopic:	Feedstock, Crystallisation, Wafering, Defect Engineering
Event:	35th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2BO.2.3
Pages:	346 - 349
ISBN:	3-936338-50-7
Paper DOI:	10.4229/35thEUPVSEC20182018-2BO.2.3
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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In the last few years, it has been found that solar cells made using p-type multicrystalline silicon (mc-Si) wafers degrade under illumination at elevated temperatures. This degradation is commonly known as light- and elevated temperature-induced degradation (LeTID) or carrier-induced degradation (CID). CID is the main challenge for the introduction of mc-Si passivated emitter and rear cells (PERC) in mass production. Previous models of the CID kinetics are based on the presence of two defects (fast and slow), neglecting the simultaneous regeneration that may occur during the degradation. Recently, it has been reported that similar degradation can be observed under anneal at moderate temperatures, even without illumination. In this work, we developed and successfully validated a new model based on the presence of only one defect and on the simultaneous degradation and regeneration processes. The model is much simpler than the current available in the literature. We use this model to investigate the impact of thermal treatment in the dark on p-type mc-Si wafers. We find that high temperatures lead to faster degradation and regeneration rates, while the degradation extent is larger at low temperatures. The activation energies of the degradation and regeneration processes are obtained from the proposed model and found to be 1.08 ± 0.05 eV and 1.11 ± 0.04 eV, respectively. Interestingly, at the end of the dark anneal process, the samples treated at high temperatures show improvement of ~40% in their effective lifetimes.