In this study, the effects of irradiation by proton beam of a plasma focus device with 5 kJ discharge energy on photovoltaic (PV) cells were investigated. Before and after irradiation, the I–V curve of the cells was measured. Changes in Voc and Isc of silicon-type PV cells were recorded. After 1, 2, 4 and 8 shots, on average compared to the initial conditions, the voltage decreased by 76.81%, 76.70%, 84.94% and 83.74% respectively, and the current decreased by 43.18%, 54.91%, 67.49% and 58.07% respectively. The behavior of the plasma focus device was simulated by the LEE code, and the damage caused by the protons of the plasma focus device in each shot was evaluated by SRIM & TRIM software. For each shot of the plasma focus device, on average, about 3.82% of the atoms were displaced. The recovery time of the crystal structure, and the improvement of photovoltaic cells’ properties after irradiation were investigated experimentally. After 10 days of irradiation, the open circuit voltage of the cells that were irradiated by 1, 2 and 4 shots were increased by 22.81, 18.00 and 35.10%, respectively. Also, the short-circuit current of the cells were increased by 7.37, 8.91 and 27.89%, respectively.