Passivation analysis of the Emitter and selective back surface field of silicon solar cells

Abstract

In this work the high-quality passivation of p-type Si solar cells with a boron-aluminum selective back surface field (BSF) and dry thermal SiO2 layers on both surfaces is analyzed comparing the internal quantum efficiency (IQE) and the current-voltage parameters. This structure may be a viable substitute for the industry's standard solar cell, which has to be reconsidered when faced with the bowing problem. We observed that increasing oxidation temperature decreases IQE for short wavelengths (400 nm), while for long wavelengths (1000 nm) the IQE increases for temperatures lower than 860 °C. The same trend is observed for the solar cells' open circuit voltages, indicating that rear surface passivation increases for thicker oxides. The short-circuit current density was affected by the higher reflectance caused by the SiO2 layer. However, by adjusting the TiO2 anti-reflective coating thickness we were able to avoid this effect, achieving solar cells with efficiencies up to 16.8 %, which is comparable to the current efficiency of cells with AI-BSF covering the whole back surface. Furthermore, no bowing was observed for this structure.