Impacts of spatially reduced grain boundary recombination regions on multicrystalline silicon solar cell performance

Abstract

In this work, we demonstrate that grain boundaries (GBs) in multicrystalline silicon solar cells may be easily grooved using porous silicon (PS). We then use this interesting property to try reducing the area of these highly recombining regions. To reach this objective a thin PS layer was formed on both front and back sides of the multicrystalline material. After removing the PS films, conventional phosphorus diffusion was achieved. Grooved GBs enable deep penetration of phosphorus and metallic contacts. As a result, we found an improvement of the I–V characteristics under the dark and at AM1.5 illumination. The light-beam-induced current was found to be improved of approximately 16% resulting from an enhancement of the bulk minority carrier collection probability. The internal quantum efficiency was also found to be enhanced by approximately 15% in a rather wide spectral range, approximately between 600 and 1100 nm. These results are discussed and compared to solar cells based on untreated multicrystalline silicon wafers.