Ultrafast in-line capable regeneration process for preventing light induced degradation of boron-doped p-type Cz-silicon PERC solar cells

Solar cells based on boron-doped p-type Czochralski-grown silicon (Cz-Si) substrates suffer from light-induced degradation (LID) which is related to a metastable boron-oxygen defect and limits the achievable cell efficiency significantly, but can be eliminated by carrier injection at elevated temperatures within a so-called regeneration process. We have developed an ultrafast regeneration process (UFR) to prevent up to 98% of the LID effect in less than 4 seconds process-time. The technology behind this process has been implemented in an in-line prototype tool with belt speeds of up to 8000 mm/min. Compared to competing techniques the technology introduced here enables tools with smaller footprint and broader process window, offering irradiation intensities up to 1 MW/m² and temporal and spatial modulation of the irradiation intensity with up to 100 Hz. Undistorted in-situ temperature measurements can be acquired via commercially available thermographic imaging equipment. Further, we introduce a new parameter called regeneration completeness in order to allow benchmarking for BO-regeneration processes. It quantifies the effectiveness of BO-regeneration processes independent of the overall efficiency in order to allow a direct comparison of the quality of different regeneration processes.