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 feld-assisted recombination. The influence of the material
on these currents has also been investigated. ( 1998 Elsevier Science B.V. All rights reserved.