Abstract Modeling the current density–voltage ( J– V) curve of a-Si:H p-i-n diodes requires a group of input physical parameters that have to be previously determined. Some of them can be determined directly from experiment, while others, as the trap cross-section, have to be indirectly determined or assigned. We present a simple procedure to estimate trap cross-section using computer simulation and parameter extraction. The experimental J– V forward characteristic of the p-i-n diode, dark and illuminated, is used to determine the ideality factor n and the short circuit current density J SC. The charged trap cross-section and its relation to the neutral trap cross-section are determined by fitting to tabulated and graphical results from simulation. Determined values of trap cross-section are used to simulate the reverse current of diodes under illumination and results compared with experimental curves.