Low-Temperature Back-Surface-Field Structures Applied to Crystalline Silicon Solar Cells: Two-Step Growth with Hydrogen Plasma Treatment for Improving the Reproducibility

摘要

We sometimes observe poor internal quantum efficiency (IQE) in the long-wavelength region of p-type single-crystalline silicon (c-Si) solar cells having back-surface-field (BSF) layers made of p-type hydrogenated amorphous silicon (a-Si:H). We found that this poor IQE is caused by the appearance of a polycrystalline phase (PP) in a-Si:H. We showed that two-step growth of BSF structures with hydrogen plasma treatment (HPT) is effective for achieving a high performance of BSF with improved reproducibility. First, a-Si:H layers were prepared on c-Si substrates at a high growth rate to suppress the appearance of PP, and consequently, the defects at the a-Si:H/c-Si interface induced by the higher growth rate were effectively passivated by HPT. Finally, a-Si:H was deposited as a capping layer on the first a-Si:H layer after HPT. We will discuss the passivation mechanism of interface defects with HPT using the data of the hydrogen profile in the a-Si:H layers treated by hydrogen plasma.