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Detecting efficiency-limiting defects in Czochralski-grown silicon wafers in solar cell production using photoluminescence imaging

: Haunschild, J.; Reis, I.E.; Geilker, J.; Rein, S.


Physica status solidi. Rapid research letters 5 (2011), Nr.5-6, S.199-201
ISSN: 1862-6254
ISSN: 1862-6270
Fraunhofer ISE ()
PV Produktionstechnologie und Qualitätssicherung; Silicium-Photovoltaik; Charakterisierung; Zellen und Module

Only recently, methods for quality control of multicrystalline silicon wafers have been published, which allow the efficiency of solar cells to be predicted precisely from photoluminescence (PL) images taken in the as-cut state. In this letter it is shown that oxygen precipitates, present in standard Czochralski silicon wafers, can cause efficiency losses of more than 4% (absolute) within an industrial solar cell proc- ess. These efficiency losses correlate with ring-like defect structures of reduced intensity in the PL image. In comparison with QSSPC-based lifetime measurements, we introduce a PL-based method of quality control which allows the critical wafers to be identified and sorted out reliably at an early state of production and thus increases yield and average efficiency of production lines.