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HL: Halbleiterphysik

HL 42: Photovoltaik II

HL 42.8: Talk

Friday, March 30, 2001, 13:15–13:30, S6

Investigtion of Carrier Lifetime in p-type Czochralski-Silicon (Cz-Si): Specific Limitations and Realistic Prediction of Cell Performance — •S. Rein, W. Warta, and S.W. Glunz — Fraunhofer ISE, Oltmannsstr. 5, 79100 Freiburg

The results from a comprehensive investigation of carrier lifetime in p-type Cz-Si confirme that the metastable defect causing the lifetime degradation in boron-doped Cz-Si (B-Cz-Si) is correlated with boron and oxygen. While no degradation and excellent lifetimes close to the theoretical limit are observed for all gallium-doped samples, the stable degraded lifetime of B-Cz-Si 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. For a high efficiency RP-PERC solar cell the maximum stable efficiency is predicted for a base doping of 5· 10¹⁵ cm⁻³ using B-Cz-Si, which could be verified experimentally.