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Investigation of carrier lifetime in p-type Cz-silicon: Specific limitations and realistic prediction of cell performance

: Rein, S.; Warta, W.; Glunz, S.W.

Volltext urn:nbn:de:0011-b-796801 (318 KByte PDF)
MD5 Fingerprint: 73a721482ea426f8b0aa01ea0e797775
Erstellt am: 31.10.2012

IEEE Electron Devices Society:
Twenty-Eighth IEEE Photovoltaic Specialists Conference 2000. Conference record : Anchorage Hilton Hotel, Anchorage, AK, 15 -22 September 2000
Piscataway: IEEE Operations Center, 2000
ISBN: 0-7803-5772-8
ISBN: 0-7803-5773-6
ISBN: 0-7803-5774-4
Photovoltaic Specialists Conference <28, 2000, Anchorage/Alaska>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()

Recent studies have revealed that the metastable defect causing the lifetime degradation in standard boron-doped Czochralski silicon (B-Cz-Si) is correlated with boron and oxygen. This is confirmed by our results from a comprehensive investigation of carrier lifetime in p-type Cz-Si. While no degradation and excellent lifetimes close to the theoretical limit are observed for all gallium-doped samples, the stable degraded lifetime of the B-Cz-Si samples is strongly reduced by the Cz-specific defect. In order to allow realistic simulations of cells from B-Cz-Si, the measured doping dependence of the bulk lifetime in B-Cz-Si is modeled by a simple empirical expression. It is demonstrated that the optimal doping concentration leading to maximum efficiency is strongly shifted with the used solar cell structure and the actual degradation state. While the maximum stable efficiency for a high efficiency RP-PERC solar cell is predicted for a base doping of 5x10(exp 15) cm-3 using B-Cz-Si, the optimal value for an industrial cell with screen printing emitter varies between 10(exp 15) cm-3 for a cell with boron BSF and 10(exp 16) cm-3 for a cell without BSF. The physical background leading to these optima is discussed in detail. Finally we verified the theoretical predictions for the high efficiency cell structure fabricating RP-PERC cells on B-Cz-Si.