Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Microcracks in silicon wafers II: Implications on solar cell characteristics, statistics and physical origin

: Demant, M.; Welschehold, T.; Kluska, S.; Rein, S.

Postprint urn:nbn:de:0011-n-3791024 (1.4 MByte PDF)
MD5 Fingerprint: a86167f49e25b0266cb17459cc4e3cb0
© IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Created on: 7.7.2016

IEEE Journal of Photovoltaics 6 (2016), No.1, pp.136-144
ISSN: 2156-3381
Journal Article, Electronic Publication
Fraunhofer ISE ()
PV Produktionstechnologie und Qualitätssicherung; Silicium-Photovoltaik; Charakterisierung von Prozess- und Silicium-Materialien; Messtechnik und Produktionskontrolle; micro-crack; electroluminescence; photoluminescence; shunt; cell

Microcracks that are induced in early processing stages, especially before emitter diffusion, strongly influence the current-voltage (I-V) characteristics of the solar cell. We focus on the impact of crack morphology measured by photoluminescence imaging in the as-cut stage on the electrical solar cell parameters. To provide a sufficient statistical base, microcracks are intentionally induced in a well-defined way in multi- (mc-Si) and mono- (Cz-Si) crystalline silicon wafers in the as-cut stage, the damaged wafers being processed to solar cells afterwards. From the dataset, a sorting criterion for microcracks concerning their electrical impact is derived, which depends on wafer thickness and material type. It is shown that cracks above 4 mm2 lead with high probability to severe shunts and, thus, need to be sorted out. Investigations by means of scanning electron microscopy (SEM) and electron-beam induced current (EBIC) measurements reveal that shunts with very low parallel resistance in Cz-Si solar cells can be attributed to metal-to-metal contacts between front and rear sides of the solar cell. Moreover, it is shown that the reduced robustness of Cz-Si compared with mc-Si concerning the formation of shunts at microcracks originates from a widening of the crack channels above 10 μm in alkaline texturing, which facilitates the formation of metal-to-metal contacts.