Lithium-doped radiation resistant silicon solar cells

It is well known that impurities in silicon interact with radiation-induced vacancies to produce complexes which are stable at room temperature. For example, there are the vacancy-oxygen and vacancy-phosphorus centers produced in n-type silicon by electron irradiation. These centers modify the electrical properties of the material, primarily by decreasing the minority-carrier lifetime. Consequently, when devices such as solar cells are irradiated, the characteristics of the device are severely degraded. This talk will present evidence that when lithium is used as the dominant impurity in silicon, the production of recombination centers is reduced. This results in solar cells with an improved radiation resistance. This study has been performed on solar cells with the diffused p on n-type base configuration. It was found that under certain conditions the use of lithium in the above cell has led to a radiation resistance to 1 MeV electrons superior to even standard n-on-p solar cells, heretofore, the most radiations-resistant cell.