Atomic-layer-deposited (ALD) Al2O3 is well-known as outstanding surface passivation material for crystalline silicon (c-Si) solar cells and is used as such in PERC cells in industry. Nevertheless, the photovoltaic (PV) community is starting to progress towards more efficient c-Si solar cell architectures, which comprise passivating contacts, such as polycrystalline silicon (poly-Si). Preliminary results have pointed out a new application for Al2O3 in this emerging field: as (sacrificial) capping layer, ALD Al2O3 greatly improves passivating contact properties.
The goal of this project is to pave the way for application of ALD Al2O3 as sacrificial capping layers in the c-Si PV industry, as this is of high importance to Dutch ALD equipment manufacturers. To achieve this, this project aims at a clear fundamental understanding as well as the in depth investigation of the benefits of ALD Al2O3 capping layers for several emerging passivating contact schemes.
The TU/e and TUD will study the fundamental working principles of capping by ALD Al2O3, such as the hydrogenation of passivating contacts and their interface with c-Si. Advanced analysis procedures and techniques such as isotope labeling, secondary ion mass spectroscopy and effusion experiments will be used to this end. Moreover, the effects of hydrogenation by ALD Al2O3 on the passivating contact properties will be monitored for the most relevant passivating contact materials for upcoming c-Si solar cells, most prominently n- and p-type poly-Si. Together with ECN and Levitech the potential for ALD Al2O3 as capping layer in PV industry will be mapped, e.g., by investigating which solar cell architectures can benefit (most) from the hydrogenation.
The AAA project will clearly demonstrate the potential and fundamental working principles of ALD Al2O3 as hydrogenation layer for passivating contact materials. The results will be disseminated in peer-reviewed journal articles and at PV conferences and will successively serve as showcase for the introduction of (sacrificial) ALD Al2O3 capping layers in PV industry. This new application for ALD Al2O3 will further strengthen the market position of Dutch ALD equipment manufacturers. Moreover, the project will enable the improvement of the quality of passivating contacts, and in this way will contribute to the increase of the energy yield of high-efficiency commercial c-Si PV modules.