Introduction of deep level defects during thermal diffusion of phosphorous (P) in silicon (Si) using spin-on-doping (SOD) from phosphosilicate glass (PSG) was studied using deep level transient spectroscopy (DLTS). The structure was utilized as a solar cell and defect-induced-degradation of the cell efficiency was studied and modeled. The light current-voltage (LIV) measurements performed on as-fabricated solar cell yielded open circuit voltage, short-circuit current density, fill factor (FF) and efficiency to be 540 mV, 24 mA/cm(2), 40% and 5%, respectively. Whilst the simulation of the similar solar cell using AFORS-HET software revealed significantly higher data than the experimental ones. However, by including three deep level defects H(1)-H(3) (holes) having activation energies (eV) 0.23, 0.33 and 0.41 in the modeled solar cell, the simulated results were observed in remarkably good agreement with experimental data. Our DLTS measurements practically witnessed H(1)-H(3) defect levels in p-layer of the cell. (C) 2011 Elsevier B.V. All rights reserved.