The superlinearity of the short-circuit current of low-resistivity-concentration solar cells

It has been observed that Si solar cells respond superlinearly to irradiance while GaAs behaves linearly. Computer analysis of superlinear characteristics of short-circuit current with irradiances above 1 sun for low-resistivity Si concentrator cells has shown the importance of the base electric field in enhancing the collection efficiency of minority carriers generated in the base region. The effect of the base electric field can be incorporated into effective upstream and downstream diffusion lengths. The effective downstream diffusion length increases from 223 μm at one sun to near 1000 μm at 1000 suns in one case. Collection of minority carriers in the base alone due to the enhanced diffusion lengths is sufficient to explain the observed superlinearity