Title:	LID-Free PERC + Solar Cells with Stable Efficiencies Up to 22.1%
Author(s):	B. Lim, A. Merkle, R. Peibst, T. Dullweber, Y. Wang, R. Zhou
Keywords:	Czochralski (Cz), Simulation, PERC, Silicon, LID
Topic:	Silicon Cells
Subtopic:	Homojunction Solar Cells
Event:	35th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2BO.3.2
Pages:	359 - 365
ISBN:	3-936338-50-7
Paper DOI:	10.4229/35thEUPVSEC20182018-2BO.3.2
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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We evaluate the potential of advanced B-doped Cz-Si with extremely low oxygen concentration ([Oi]) of 2.6 ppma as well as Ga-doped Cz-Si to avoid light-induced degradation (LID) in state-of-the-art bifacial PERC+ solar cells. We compare these materials to current industry standard B-doped Cz-Si with [Oi] between 12 and 16 ppma.. We measure the solar cell efficiency and the lifetime of samples processed in parallel to the solar cells in three important states: as-processed, after illumination at room temperature (degraded), and after illumination at elevated temperature (regenerated). In the as-processed state, the low [Oi] as well as the Ga-doped solar cells yield 0.2%abs to 0.3%abs higher efficiencies than the industrial B-doped Cz-Si. In addition, their efficiency is stable under illumination at room temperature. Furthermore, the measured bulk lifetimes are used as input parameters in a device simulation. Subsequently, we compare the simulated solar cell efficiencies to the measured efficiencies. For the industry standard B-doped Cz-Si, the simulation predicts 0.7%abs loss due to LID, which fits to the experimental result. After regeneration, the device simulation predicts an increase by 0.4%abs compared to the as-processed state, whereas the measured PERC+ efficiency improves only to the as-processed level. We discuss possible reasons for this discrepancy.