Avoiding boron-oxygen related degradation in highly boron doped Cz silicon

Abstract

Lifetime degradation in Cz-grown silicon due to the formation of recombination active complexes consisting of boron and oxygen limits the efficiency potential of Cz-Si solar cells. In this contribution, a new approach to avoid this special type of degradation is presented. It is shown that there exists an additional state of the complex beside the ‘annealed’, weak recombination active state and the lifetime limiting, ‘degraded’ state, which is stable under the typical working conditions and, more important, only weakly recombination active. A simple model based on observations as well as some properties of this so called ‘regenerated’ state and its formation kinetics will be presented.