TY - JOUR

T1 - Possible candidates for impurities in mc-Si wafers responsible for light-induced lifetime degradation and regeneration

AU - Bredemeier, Dennis

AU - Walter, Dominic C.

AU - Schmidt, Jan

N1 - The authors thank C. Marquardt for sample processing. This work was funded by the German State of Lower Saxony and the German Federal Ministry of Economics and Energy and by industry partners within the research project “SolarLIFE” (Contract no. 0325763C). The content is the responsibility of the authors.

PY - 2018/1/15

Y1 - 2018/1/15

N2 - We examine the light-induced carrier lifetime degradation and regeneration at elevated temperature in multicrystalline silicon (mc-Si) wafers of different thicknesses. The experimental results show that the thinner the wafer the less pronounced the degradation is and the faster the regeneration takes place. We interpret this result in the framework of a recently proposed defect model, where the lifetime regeneration is attributed to the diffusion of the recombination-active impurity to the wafer surfaces, where it is permanently trapped. Modeling the measured thickness-dependent lifetime evolutions enables us to determine the diffusion coefficient of the impurity to be in the range (5 ± 2) × 10 −11cm 2 s −1 at a temperature of 75 °C. Comparing the diffusion coefficient extracted from our measurements with data published in the literature allows us to exclude most impurities. Despite the large uncertainties in the diffusion coefficient data reported in the literature, reasonable agreement is only obtained for nickel, cobalt, and hydrogen. One important practical implication of our study is that mc-Si wafers thinner than 120 μm do not suffer from pronounced light-induced lifetime degradation.

AB - We examine the light-induced carrier lifetime degradation and regeneration at elevated temperature in multicrystalline silicon (mc-Si) wafers of different thicknesses. The experimental results show that the thinner the wafer the less pronounced the degradation is and the faster the regeneration takes place. We interpret this result in the framework of a recently proposed defect model, where the lifetime regeneration is attributed to the diffusion of the recombination-active impurity to the wafer surfaces, where it is permanently trapped. Modeling the measured thickness-dependent lifetime evolutions enables us to determine the diffusion coefficient of the impurity to be in the range (5 ± 2) × 10 −11cm 2 s −1 at a temperature of 75 °C. Comparing the diffusion coefficient extracted from our measurements with data published in the literature allows us to exclude most impurities. Despite the large uncertainties in the diffusion coefficient data reported in the literature, reasonable agreement is only obtained for nickel, cobalt, and hydrogen. One important practical implication of our study is that mc-Si wafers thinner than 120 μm do not suffer from pronounced light-induced lifetime degradation.

KW - carrier lifetime

KW - degradation

KW - diffusion

KW - multicrystalline silicon

UR - http://www.scopus.com/inward/record.url?scp=85083621171&partnerID=8YFLogxK

U2 - 10.1002/solr.201700159

DO - 10.1002/solr.201700159

M3 - Article

VL - 2

JO - Solar RRL

JF - Solar RRL

IS - 1

M1 - 1700159

ER -