Effect of hydrogenation on minority carrier lifetime in low-grade silicon

Silicon p–n junctions for solar cell applications were prepared by growing thin n-type films on p-type metallurgical-grade silicon (MG-Si) substrate in a liquid solution of arsenic-doped gallium/indium solution. MG-Si has much higher impurity concentrations than traditional solar-grade silicon, but is here being used as a low-cost alternative. The as-grown film showed negligible photovoltaic response. A post-growth exposure of the as-grown p–n junctions to a H2/Ar plasma resulted in an active photovoltaic device with VOC of up to several hundred mV. Furthermore, a significant increase in the minority carrier lifetime was observed. The short-circuit current density indicated low efficiency in accordance with the high defect concentration of the impure substrate. An x-ray diffraction study of MG-Si prior to and after film growth revealed textured crystal structure that diminished during film growth, indicating that the film is more homogeneous than the substrate.