P-type Upgraded Metallurgical-Grade Multicrystalline Silicon Heterojunction Solar Cells with Open-Circuit Voltages over 690 mV

摘要

Herein, low-cost p-type upgraded metallurgical-grade (UMG) multicrystalline silicon wafers are processed from the edge of the silicon cast using a multi-stage defect-engineering approach, incorporating gettering and hydrogenation to improve the wafer quality. Significant reductions in the concentration of interstitial iron and improvements in the bulk lifetime from 15 to 130 mu s are observed. Subsequently, all the surface layers are removed and silicon heterojunction solar cells are fabricated. The cells exhibit an efficiency of 18.7%, and open-circuit voltages over 690 mV is formed using wafers with initial lifetimes of <15 mu s. This demonstration of such high voltages, the highest recorded for this material to date, indicates the power of the gettering and hydrogenation processes used and the potential of p-type UMG silicon to fabricate heterojunction solar cells and other solar cell technologies capable of high open-circuit voltages.