Performance improvements of solar-grade crystalline silicon by continuously variable temperature phosphorous gettering process using a porous silicon layer

Abstract

The Continuously Variable Temperature Phosphorous Gettering process using a Porous Silicon Layer (PSL-CVTPG) was proposed. PSL-CVTPG process can getter unwanted impurities from Solar-Grade silicon (SOG-Si) wafers and upgrade photovoltaic properties of solar cells more efficiently than conventional Constant Temperature Phosphorus Gettering process using a Porous Silicon Layer (PSL-CTPG). The resistivity, and mobility of majority carriers, and the effective lifetime of minority carriers were evaluated; the results showed that under certain conditions, the gettering effect of the PSL-CVTPG is better than that of the optimum PSL-CTPG. By orthogonal experiments, the optimum PSL-CVTPG conditions were found to be 900 °C/60 min+750 °C/60 min. PSL-CVTPG and CTPG processes under their respective optimum gettering conditions were used in the fabrication of solar cells, and cells based on SOG-Si wafers purified by the PSL-CVTPG process exhibited an amelioration in photovoltaic performances.