Browsing by Author "Heinz, Friedemann D."

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Moving Beyond p-Type mc-Si: Quantified Measurements of Iron Content and Lifetime of Iron-Rich Precipitates in n-Type Silicon
(2018) Morishige, Ashley E.; Heinz, Friedemann D.; Laine, Hannu S.; Schon, Jonas; Kwapil, Wolfram; Lai, Barry; Savin, Hele; Schubert, Martin C.; Buonassisi, Tonio
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
N-type multicrystalline silicon (mc-Si) is a promising alternative to the dominant p-type mc-Si for solar cells because it combines the cost advantages of mc-Si while benefiting from higher tolerance to transition metal contamination. A detailed understanding of the relative roles of point defect and precipitated transition metals has enabled advanced processing and high minority carrier lifetimes in p-type mc-Si. This contribution extends that fundamental understanding to Fe contamination in n-type mc-Si, helping enable processing of this material into an economical and high-performance photovoltaic device. By directly correlating micro-photoluminescence-based minority carrier lifetime mapping and synchrotron-based micro-X-ray fluorescence mapping of Fe-rich precipitates, we develop a quantitative, physical understanding of the recombination activity of Fe-rich precipitates in n-type mc-Si.
Passivation of black silicon boron emitters with atomic layer deposited aluminum oxide
(2013) Repo, Päivikki; Benick, Jan; von Gastrow, Guillaume; Vähänissi, Ville; Heinz, Friedemann D.; Schön, Jonas; Schubert, Martin C.; Savin, Hele
School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The nanostructured surface – also called black silicon (b-Si) – is a promising texture for solar cells because of its extremely low reflectance combined with low surface recombination obtained with atomic layer deposited (ALD) thin films. However, the challenges in keeping the excellent optical properties and passivation in further processing have not been addressed before. Here we study especially the applicability of the ALD passivation on highly boron doped emitters that is present in crystalline silicon solar cells. The results show that the nanostructured boron emitters can be passivated efficiently using ALD Al2O3 reaching emitter saturation current densities as low as 51 fA/cm2. Furthermore, reflectance values less than 0.5% after processing show that the different process steps are not detrimental for the low reflectance of b-Si.