Single-crystal Si solar cells with pulsed-DC sputtered SiNx:H anti-reflection film and phosphoric-acid-diffused n+ emitter

Abstract

A low-environmental-load single-crystal Si solar-cell fabrication method was demonstrated, in which SiNx:H anti-reflection film was formed using a pulsed-DC reactive sputtering method with Ar and a forming gas (FG: 3.8% H2 in N2), and an n+ emitter was created using thermal diffusion of diluted phosphoric acid. In the SiNx:H film, it was shown that both exposure of the Si surface to FG plasma and FG annealing of the SiNx:H film dramatically decreased the surface recombination velocity, S, of the Si substrate, because of an improved Si/SiNx:H interface. The interface state density was found to be 2.1 × 1011 cm−2·eV−1 and the minimum S was 72 cm·s−1; these values are comparable to those obtained using the plasma-enhanced chemical vapor deposition method. The characteristics of the fabricated solar cells were: a short-circuit current of 38.1 A·cm−2, open-circuit voltage of 594.6 V, fill factor of 73.8, and an energy conversion efficiency of 16.7%.