The effects of low-energy proton-induced degradation of photovoltaic properties and generation of deep-level defects in n(+)/p InGaP solar cells have been investigated. Energy-dependent effects included decreased solar cell efficiency and increase the carrier removal rate with decreasing proton energy. The spectral response depicts that the degradation is more at longer wavelengths with the increase of proton fluence. A new majority (hole) trap HP1 has been observed in low-energy proton irradiated p-InGaP at 0.90+/-0.05eV above the valence band for the first time. The carrier removal rates were found to be 61433 and 8640 cm(-1) for 100 and 380-keV proton irradiation, respectively. (C) 2002 Published by Elsevier Science B.V.