High minority carrier lifetime in phosphorus-gettered multicrystalline silicon

Abstract

The electronic quality of multicrystalline material produced by directional solidification has been evaluated by means of photoconductance techniques. Very high minority carrier lifetimes, in the vicinity of 200 μs, have been measured in p-type 1.5 Ω cm material that had received a phosphorus diffusion gettering treatment. The measurements correspond to an effective lifetime averaged over an area of 3 cm2 that includes several grain boundaries and reflects the combined bulk, grain boundary and surface recombination mechanisms. The high lifetime (15 μs) also obtained in low resistivity 0.2 Ω cm wafers has allowed the fabrication of solar cells with an open-circuit voltage of 657 mV (AM1.5 G, 100 mW/cm2, 25 °C), probably the highest ever reported for multicrystalline silicon.