The minority-carrier diffusion length in the base region of p+-n (n+-p) junction solar cells has been deduced from the relative spectral response in the long wavelength. The doping and temperature dependences of minority-carrier diffusion length have also been characterized. It has been shown that the minority-carrier diffusion length is slightly increased with increasing temperature and is decreased with increasing doping concentration. Based on the known minority-carrier diffusivity as functions of doping concentration and temperature, the doping and temperature dependences of minority-carrier lifetimes have been deduced. It has been verified that the empirical relationship between minority-carrier lifetime and doping concentration deduced by other method is in good agreements with our experimental measurements. Moreover, it has been shown that the minority-carrier lifetime is increased with increasing temperature, which is consistent with that measured by the open-circuit voltage decay (OCVD) method.