Using SRIM to calculate the relative damage coefficients for solar cells

It is shown how the widely available computer code SRIM can be used to calculate proton relative damage coefficients (RDCs) for solar cells. This approach is important in cases when the incident proton energy is reduced significantly in traversing the active volume of the cell and, consequently, when analytic calculations of the nonionizing energy loss (NIEL) are not satisfactory for calculating the energy dependence of the RDCs. In the SRIM approach it is assumed that the RDCs are proportional to the total number of vacancies formed. The calculation involves integrating the ‘vacancy.txt’ files produced by SRIM over the active depth of the cells and normalizing the results to the number of total vacancies produced by 10 MeV protons. The RDCs calculated from SRIM are found to agree well with experimentally measured values for both Si and multijunction (MJ) solar cells. Copyright © 2005 John Wiley & Sons, Ltd.