Atomic layer deposition of Al2O3 for industrial local Al back-surface field (BSF) solar cells


By Aude Rothschild, IMEC; Bart Vermang, IMEC; Hans Goverde, IMEC

Al2O3 deposition has received a lot of attention in the last few years for its attractive passivation properties of c-Si surfaces. Within the local Al back-surface field (BSF) cell concept, we considered several avenues of study: surface preparation, thermal stability, charge investigation and the ‘blistering’ phenomenon. The investigations converged on a passivation stack that includes a thin interfacial SiO2 like layer and a thin Al2O3 layer (~10nm), which undergoes a high-temperature anneal (> 600°C). In order for a surface passivation with Al2O3 to be a cost-effective step for the PV industry, a high Al2O3 deposition rate is required. Compared to the different high-throughput tools that have recently emerged on the PV market, such as atomic layer deposition (ALD) and plasma-enhanced chemical vapour deposition (PECVD), our tool screening revealed quite similar results. The differences therefore seem to have an origin primarily in the tool specifications rather than in the achievable Al2O3 material properties.

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Our largest issue to date at 224 pages, the 13th edition of the Photovoltaics International journal features a focus on myriad topics including wafering and wire-sawing thermodynamics, the passivation benefits of ALD, reactive magnetron sputtering, PV module degradation and inverter certification. Contributors include imec, Fraunhofer IST, Motech Industries, PI Berlin, University of Toledo and CH2M HILL.

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