Title:	WetAlOx: A Novel, Cost Effective, Negative Charge Passivation Method for Crystalline Silicon Solar Cells
Author(s):	E. Schmid, S. Schmitt, T. Boescke, E. Wefringhaus, F. Buchholz, C. Peter, R. Marczak, A. Ramakrishnan, M. Mateescu, P. Kunze
Keywords:	Passivation, Impurities, Al2O3, PERC, PERT
Topic:	Silicon Cells
Subtopic:	Homojunction Solar Cells
Event:	35th European Photovoltaic Solar Energy Conference and Exhibition
Session:	2AV.2.34
Pages:	591 - 595
ISBN:	3-936338-50-7
Paper DOI:	10.4229/35thEUPVSEC20182018-2AV.2.34
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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We present the development and evaluation of a novel negative charge passivation with cost effective aluminum oxide (Pascal). Instead of relying on vacuum processes, a thin, charge inducing aluminum oxide layer is generated by a novel wet-chemical process (“WetAlOx” process) on the silicon surface. This novel passivation layer was evaluated for state-of-the-art p-type PERC and n-type PERT solar cell concepts. The “WetAlOx” concept was investigated on cell level and precursor level with symmetrical lifetime samples. It was possible to generate negative surface charge densities (Qtot) from -4.0·1011 to -1.4·1012 cm-2 depending on process conditions. The surface charge density was mainly controlled by pH of the aluminium salt solution. By increasing the pH the surface charge density is becoming more negative. An undisered side effect of the increasing pH is the increased adsorption rates of undisired ions, which contaminate the surface. When applying a “WetAlOx” passivation stack to PERC cells the “WetAlOx” shows worse performance compared to bare silicon oxide / silicon nitride and ALD AlOx (atomic layer deposition aluminum oxide) passivation stacks. In the n-PERT cell concept the “WetAlOx” passivation stack shows comparable performance to conventional passivation methods such as silicon oxide / silicon nitride stack.