Thin N-I-P radiation resistant solar cells

Several sets of N-I-P sola cells were fabricated from high resistivity silicon to test the effectiveness of various methods for hardening these devices against radiation. Different substrate materials were used to provide information on the effects of dopant concentration, silicon type, and the presence of oxygen. In some cells, P-type float-zone refined silicon of 800, 8000 and 15,000 omega-cm resistivity was used to provide a basis for studying resistivity and purity effects. In other cells, N-type silicon (approximately 800 omega-cm) was used to allow a comparison of dopant type. Oxygen-rich, crucible-grown, silicon (approximately 100 omega-cm, p-type) will provide information on purity effects and defect gettering. Lithium was introduced into different types of silicon to determine if mobile ions can reduce radiation induced defects in high resistivity material. Thin cells (2 mil) were fabricated to study the effects of cell thickness and carrier injection on radiation damage. The electrical characteristics of the different sets of cells were measured, analyzed, and compared prior to shipment of the cells to NASA/Lewis for irradiation.