Ring Defects Associated with Boron–Oxygen‐Related Degradation in p‐Type Silicon Heterojunction Solar Cells

Silicon heterojunction (SHJ) cell architectures, which have dominated silicon single‐junction efficiency records for the past 10 years, are processed at relatively low temperatures, on the order of ≈250 °C. Recombination‐active oxygen complexes in crystalline silicon, formed from interstitial oxygen (O i ), typically require temperatures higher than this to form. Therefore, it is typically assumed that SHJ cells are immune to such defects. This contrasts with the high‐temperature passivated emitter and rear cell (PERC) and tunneling oxide passivating contact (TOPCon) architectures, which can suffer from oxygen precipitates that are recombination active and difficult to predict. Herein, ring‐like defects are observed in boron‐doped p‐type SHJ solar cells, which leads to a degradation of open‐circuit voltage. It is shown that the spatial variation of this recombination activity is related to the boron–oxygen defect, the variation of which is likely due to the radial O i distribution. Although boron‐doped p‐type wafers are no longer the industry standard, the defect engineering of wafers for SHJ production, using high‐temperature processing, is gaining significant interest. Such wafers can have an increased susceptibility to ring‐like defects. Therefore, spatially inhomogeneous defects causing recombination may become increasingly relevant for SHJ cells.