Ultrafast Regeneration – Prevention of Light-Induced Degradation in Solar Cells via Ultrafast Regeneration

Duration: September 2016 - November 2019
Contracting Authority/ Sponsors: German Federal Ministry of Economic Affairs and Energy (BMWi)
Project Partners:

Light-induced degradation can cause significant losses in crystalline silicon solar cells and module output power. The main reason for light-induced degradation in monocrystalline Cz-Si solar cells is the formation of a recombination‑active boron oxygen (BO) complex in the silicon bulk. A permanent deactivation of the recombination caused by BO complex through so-called regeneration has been known for a long time.Fast regeneration processes were reported in the past, which enable the integration of regeneration into industrial production. Fraunhofer ISE developed a regeneration process, which can prevent more than 90 % of degradation within an industrial feasible process time of seconds.

Degradation is caused by charge carrier injection, e.g., by illumination. However, for charge carrier injection at temperatures above 65 °C, a permanent deactivation of the recombination activity of the BO complex could be observed, the so-called regeneration. Conventional regeneration processes require several hours to permanently deactivate the recombination activity of all defects. However, it was also reported in the past that an increase in illumination intensity used for the regeneration process drastically reduces the process time for a deactivation of the recombination activity.

The technology for ultra-fast regeneration developed at Fraunhofer ISE uses laser-based illumination enabling very high illumination intensities. The process time for regeneration processes that avoid more than 90 % of degradation, amounts to a few seconds. These results were repeatedly achieved on Cz-Si solar cells from different manufacturers. The short process time enables an industrial throughput of more than 3600 solar cells per hour. All components used for the process exhibit a high technological readiness level and, therefore, allow immediate integration into an industrial production tool. Since September 2016, the project “UFO” (Ultra-fast Regeneration) funded within the scope of the German Federal Ministry of Economic Affairs and Energy (BMWi) has been working on integrating the technology into a pilot tool and on a deepened physical understanding of the transitions between the different states of the BO defects within very short timescales.