Direct Current Sputter Epitaxy of Heavily Doped p+ Layer for Monocrystalline Si Solar Cells

Sputter epitaxy of p+ layer for fabrication of Si solar cells (SCs) was demonstrated. Hall carrier concentration of p+ layer was 2.6 × 1020 cm−3 owing to cosputtering of B with Si at low temperature, which had enabled heavy and shallow p+ dope layer. p+nn+ SCs were fabricated and influence of p+ and n+ layers was investigated. Internal quantum efficiency (IQE) of p+nn+ SCs was 95% at visible light and was larger than 60% at ultraviolet (UV) light when the p+ layer was thinner than 30 nm. At near infrared (NIR), extra increment on IQE was achieved by rear n+ back surface field (BSF) layer with a thickness thinner than 100 nm