In this work, we study the effect of irradiation as in low Earth orbits on heterojunction technology structures (p)a-Si:H/(n)c-Si. The samples were irradiated with an electron beam with an energy of 2 MeV and fluences of 3·1013cm–2 to  3·1015cm–2. Solar cells performance deteriorate with increasing of fluence due to decrease of lifetime of charge carriers in bulk silicon. According to DLTS measurements, three defects with activation energies of 0.18 eV, 0.25 eV  and 0.43 eV were detected, and their nature was identified. Further, the concentrations of the found defects were analyzed, during which it became clear that the concentration of defects decreases with increasing depth of the  investigated structure. The correlation between fluence and concentration is also visible. The average values of concentrations vary from 1012 to 1014.