The current-voltage characteristics of solar cells, under illumination and in the dark, represent a very important tool for characterizing the performance of the solar cell. The PC-1D computer program has been used to analyze the deviation of the dark current-voltage characteristics of p-n junction silicon solar cells from the ideal two-diode model behavior of the cell, namely the appearance of "humps" in the I-V characteristics. The effects of the surface recombination velocity, the minority-carrier lifetimes in the base - and emitter regions of the solar cell, as well as the temperature dependence of the I-V characteristics have been modeled using PC-1D. It is shown that the "humps" in the I-V characteristics arise as a result of recombination within the space-charge region of the solar cell, occurring when conditions for recombination are different from the simple assumptions of the Sah-Noyce-Shockley theory.