In the presented work the growth and fabrication process of dilute nitride based solar cells were reported. We fabricated three different solar cells to investigate the influence of top contact on their electrical parameters. Test devices were characterized by the means of current–voltage measurements carried out under the sunlight simulator. The obtained I–V results were scrutinized using a single diode equivalent circuit of a solar cell. We employed the Lambert W approach to find the solvable solution of the modified Shockley equation, in order to determine the basic solar cell electrical parameters such as: ideality factor n, series and shunt resistances (Rs and Rsh), saturation current I0 and photocurrent Iph generated in the solar cell structure. It was found that electrical parameters obtained from the fitting procedure depend on solar cell design. The type of top electrode influences the values of parasitic resistances, open circuit voltage and short circuit current.