Conduction processes in silicon solar cells

Dark I-V experiments have been performed on directional solidification (DS), Czochralski (CZ) and cold crucible casting (CCC) silicon solar cells. Series and shunt resistances, ideality factors and saturation currents have been determined. However the usual equations (recombination and diffusion current) cannot fit some cells maybe because they are too approximated or because other mechanisms are present. The aim of this work is to explain the mechanisms occurring in these cells and to correlate them with the device characteristics. We show that for some solar cells we must add to the usual two exponential model (diffusion and recombination) trap assisted tunneling current and field assisted recombination. The influence of the material on these currents has also been investigated.