Impact of the firing temperature profile on light induced degradation of multicrystalline silicon. Issue 12 (26th October 2016)

• Record Type: Journal Article
• Authors: Eberle, Rebekka; Kwapil, Wolfram; Schindler, Florian; Schubert, Martin C.; Glunz, Stefan W.
• Is Part Of: Physica status solidi. Volume 10:Issue 12(2016)
• Page Start: 861
• Page End: 865
• Publication Date: 2016-10-26
• Subjects: multicrystalline silicon -- light‐induced degradation -- temperature profile -- heat ramp; Solid state physics -- Periodicals; 530.4105
• DOI: 10.1002/pssr.201600272
• Languages: English
• ISSNs: 1862-6254

Abstract

Abstract : Light‐ and elevated temperature‐induced degradation in multicrystalline silicon can reduce the efficiency of solar cells significantly. In this work, the influence of the firing process and its temperature profile on the degradation behaviour of neighbouring mc‐Si wafers is analysed. Five profiles with measured high peak temperatures ≥800 °C and varying heating and cooling ramps are examined. With spatially resolved and lifetime calibrated photoluminescence images, normalized defect concentrations N * t are calculated to determine the degradation intensity. Wafers that underwent a fast firing process typical for industrial solar cell production show a significantly stronger degradation than samples that were subjected to the same peak temperature but with slower heating and cooling rates. A spatially resolved analysis of the carrier lifetime in the whole wafer shows that the degradation begins in low lifetime areas around dislocation clusters, spreading into good grains after several hours. By the use of optimized ramp‐up and/or ramp‐down rates during the firing even at very high peak temperatures, light and elevated temperature induced degradation can be suppressed. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) Abstract : Light‐ and elevated temperature‐induced degradation (LeTID) in multicrystalline silicon can reduce the efficiency of solar cells significantly. The influence of the firing process and its temperature profile on LeTID of mc‐Si wafers is analysed. Wafers that underwent a fast firing process show a significantly stronger degradation than samples that were subjected to slower temperature rates. By the use of optimized temperature profiles during the firing, LETID can be suppressed.