An overview is given of various electronic effects present in polycrystalline thin film solar cells, which do not occur in standard crystalline Si solar cells. It is explained how these effects are treated numerically in a numerical solar cell simulation tool, SCAPS, developed at the author's institute. The capabilities and limitations of SCAPS are discussed. Simulation examples of current-voltage, capacitance-voltage and capacitance-frequency characteristics are given. The agreement between the simulations and measurements is shown and discussed, both for CdTe and for Cu(In,Ga)Se-2 solar cells.