A novel method to enhance the gettering efficiency in p-type Czochralski silicon by a sacrificial porous silicon layer

Abstract

A new two-step phosphorous diffusion gettering (TSPDG) process using a sacrificial porous silicon layer (PSL) is proposed. Due to a decrease in high temperature time, the TSPDG (PSL) process weakens the deterioration in performances of PSL, and increases the capability of impurity clusters to dissolve and diffuse to the gettering regions. By means of the TSPDG (PSL) process under conditions of 900°C/60 min + 700°C/30 min, the effective lifetime of minority carriers in solar-grade (SOG) Si is increased to 14.3 times its original value, and the short-circuit current density of solar cells is improved from 23.5 o 28.7 mA/cm2, and the open-circuit voltage from 0.534 to 0.596 V along with the transform efficiency from 8.1% to 11.8%, which are much superior to the results achieved by the PDG (PSL) process at 900°C for 90 min.