Browsing by Author "Calle, Eric"

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Black silicon solar cells with interdigitated back-contacts achieve 22.1% efficiency
(2015) Savin, Hele; Repo, Päivikki; von Gastrow, Guillaume; Ortega, Pablo; Calle, Eric; Garín, Moises; Alcubilla, Ramon
School of Electrical Engineering | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The nanostructuring of silicon surfaces—known as black silicon—is a promising approach to eliminate front-surface reflection in photovoltaic devices without the need for a conventional antireflection coating. This might lead to both an increase in efficiency and a reduction in the manufacturing costs of solar cells. However, all previous attempts to integrate black silicon into solar cells have resulted in cell efficiencies well below 20% due to the increased charge carrier recombination at the nanostructured surface. Here, we show that a conformal alumina film can solve the issue of surface recombination in black silicon solar cells by providing excellent chemical and electrical passivation. We demonstrate that efficiencies above 22% can be reached, even in thick interdigitated back-contacted cells, where carrier transport is very sensitive to front surface passivation. This means that the surface recombination issue has truly been solved and black silicon solar cells have real potential for industrial production. Furthermore, we show that the use of black silicon can result in a 3% increase in daily energy production when compared with a reference cell with the same efficiency, due to its better angular acceptance.
Long-term stability of Al2O3 passivated black silicon
(2016) Calle, Eric; Ortega, Pablo; von Gastrow, Guillaume; Martin, Isidro; Savin, Hele; Alcubilla, Ramon
A4 Artikkeli konferenssijulkaisussa
In this work we report on the long-term stability of black silicon surfaces passivated with atomic layer deposited (ALD) 20 nm thick Al2O3 films on p- and n-type FZ c-Si substrates. The results are directly compared with random pyramid textured counterparts. The effective surface recombination velocity Seff has been measured within a time frame of one year after activation of surface passivation. The results demonstrate that after an initial slight degradation during the first month Seff values stabilize around 45 and 25 cm/s on p- and n-type black silicon samples, respectively. These values are enough to guarantee stable high efficiency in interdigitated back-contacted (IBC) c-Si(n) solar cells (> 24.5%) using black silicon nanostructures on the front side. Similar, although weaker, losses are also observed in surface passivation on textured samples covered by Al2O3 with equal thickness, indicating that the origin of the instability might be independent of surface morphology.
Metallized Boron-Doped Black Silicon Emitters For Front Contact Solar Cells
(2018) von Gastrow, Guillaume; Calle, Eric; Ortega, Pablo; Alcubilla, Ramon; Daniil, Andreana; Stutz, Elias Z.; Fontcuberta i Morral, Anna; Husein, Sebastian; Nietzold, Tara; Bertoni, Mariana; Savin, Hele
A4 Artikkeli konferenssijulkaisussa
We study doping and metallization of black silicon (bSi) boron emitters formed by ion implantation or diffusion. We demonstrate that conformal metal layers can be deposited on bSi by electron beam evaporation. Raman spectroscopy shows that high boron concentrations (4·10 19 cm -3 ) are obtained in bSi by ion implantation, while maintaining emitter saturation current (J 0e ) below 20 fA/cm 2 with Al 2 O 3 passivation. In diffused bSi emitters, doping increases to twice the values of planar substrates, reaching values up to 7·1020 cm -3 . Those doping values allow specific contact resistivities down to (0.3 ± 0.2) mΩ·cm 2 on boron-implanted bSi surfaces with nickel or aluminum contacts.