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

Abstract

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 µs 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 µs. 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.