Spatially separated atomic layer deposition of Al2O3, a new option for high-throughput Si solar cell passivation
conference paper
A next generation material for Si surface passivation is atomic layer deposited (ALD) Al2O3. However, conventional time-resolved ALD is limited by its low deposition rate. Initially, a high-deposition-rate prototype ALD reactor based on the spatially-separated ALD principle has been developed, with Al2O3 deposition rates up to 1.2 nm/s. Later, the spatial ALD technique has been transferred to an actual in-line process development tool (PDT) for commercial high-throughput ALD of Al2O3, resulting in a deposition rate of 30 nm/min. The passivation quality and uniformity of the spatiallyseparated ALD Al2O3 films are evaluated on p- and n-type Si, applying quasi-steady-state photo-conductance, carrier density imaging and infrared lifetime mapping. In all cases, a spatial ALD Al2O3 layer of only 10 nm reached an excellent passivation quality and uniformity, comparable to reference wafers passivated by equivalent temporal plasma-assisted or thermal ALD Al2O3. Effective surface recombination velocities as low as 1.1 or 2.9 cm/s were obtained after annealing at 350 °C or firing, respectively. Using spatial ALD Al2O3 passivated local Al back surface field p-type Si solar cells, the sufficient passivation of this high-throughput Al2O3 layer is evaluated: an average gain in open circuit voltage as compared to SiOx rear passivated i-PERC cells is obtained.
TNO Identifier
436021
ISSN
10627995
Publisher
IEEE
Source title
Conference Record of the IEEE Photovoltaic Specialists Conference, 37th IEEE Photovoltaic Specialists Conference, PVSC 2011, 19 June 2011 through 24 June 2011, Seattle, WA, USA
Pages
001144-001149
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