The device parameters (carrier lifetime, ideality factor), and physical parameters (built-in voltage, doping concentration) of silicon (Si) and gallium arsenide (GaAs/Ge) solar cells are measured at different temperatures using time domain technique. Carrier lifetime is calculated from open circuit voltage decay (OCVD). Built-in voltage and doping concentration are derived from the cell capacitance measured at different bias voltages. Ideality factor is derived from the I–V characteristics of solar cell. Carrier lifetime increases while built-in voltage decreases with increase in temperature. Ideality factor of the solar cell decreases with temperature.