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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/18032

Title: Thin silicon foils produced by epoxy-induced spalling of silicon for high efficiency solar cells
Authors: Martini, Roberto
Kepa, J.
Debucquoy, M.
Depauw, V.
Gonzalez, M.
Gordon, I.
Stesmans, A.
Issue Date: 2014
Abstract: We report on the drastic improvement of the quality of thin silicon foils produced by epoxy-induced spalling. In the past, researchers have proposed to fabricate silicon foils by spalling silicon substrates with different stress-inducing materials to manufacture thin silicon solar cells. However, the reported values of effective minority carrier lifetime of the fabricated foils remained always limited to similar to 100 mu s or below. In this work, we investigate epoxy-induced exfoliated foils by electron spin resonance to analyze the limiting factors of the minority carrier lifetime. These measurements highlight the presence of disordered dangling bonds and dislocation-like defects generated by the exfoliation process. A solution to remove these defects compatible with the process flow to fabricate solar cells is proposed. After etching off less than 1 mu m of material, the lifetime of the foil increases by more than a factor of 4.5, reaching a value of 461 mu s. This corresponds to a lower limit of the diffusion length of more than 7 times the foil thickness. Regions with different lifetime correlate well with the roughness of the crack surface which suggests that the lifetime is now limited by the quality of the passivation of rough surfaces. The reported values of the minority carrier lifetime show a potential for high efficiency (>22%) thin silicon solar cells. (C) 2014 AIP Publishing LLC.
Notes: [Martini, R.; Poortmans, J.] Katholieke Univ Leuven, Dept Elect Engn, B-3001 Leuven, Belgium. [Martini, R.; Debucquoy, M.; Depauw, V.; Gonzalez, M.; Gordon, I.; Poortmans, J.] IMEC, B-3001 Leuven, Belgium. [Kepa, J.; Stesmans, A.] Katholieke Univ Leuven, Dept Phys, B-3001 Leuven, Belgium. [Poortmans, J.] Univ Hasselt, B-3500 Hasselt, Belgium.
URI: http://hdl.handle.net/1942/18032
DOI: 10.1063/1.4901026
ISI #: 000344588600081
ISSN: 0003-6951
Category: A1
Type: Journal Contribution
Validation: ecoom, 2015
Appears in Collections: Research publications

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