Back-side passivation in industrial mass-production.

Back-side passivation in industrial mass-production.

Almere, the Netherlands – November 24, 2016 – The majority of new cell designs clearly benefits from the use of Al2O3 as surface passivation (e.g. PERC, n-type, IBC). In this work, a comparison between PECVD and ALD is made based on layer integration and deposition system performance. When taking into account the intrinsic passivation properties and cost of ownership, a layer thickness of 2nm for front side and 5 to 6 nm for backside passivation are considered as good values for use in industrially produced solar cells. These thicknesses can easily be deposited using ALD, while for PECVD only thicker layers provide sufficient surface coverage and passivation. Additionally the TMA usage efficiency in ALD deposition (~30-40%) is significantly higher as compared to PECVD (~8-20%). The reason for this difference is that in the CDV chamber precursor gas mixing occurs which causes a significant deposition on the chamber walls. As a result, the maintenance cycle of the PECVD chamber is significantly shorter compared to the Levitrack ALD. But most significantly, the resulting efficiency for cells using ALD Al2O3 is above 21% while the cell results for PECVD Al2O3 are clearly lower (typically 0.3%abs) with a larger spread around average. With increasing wafer count, this spread in PECVD cell efficiencies increases towards lower values.

Poster EUPVSEC

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