The non-linear dependence of photoconductivity (PC) on wavelength and intensity of illumination was used to evaluate the lifetime and quantum efficiency coefficient of carrier photogeneration in RF sputtered thin films of a-Si:H. The change of spatial distribution of radiation intensity over the sample thickness with the change of photon energy has been taken into account. Due to this, for the photon energies greater than the semiconductor energy gap, the decay of PC with an increase of absorption coefficient of radiation could be described using only one recombination parameter : the lifetime factor proportional to carrier lifetime. The comparison of the values of absorption coefficient obtained from the measurements of optical transmittance, CPM and the quantum efficiency coefficient is presented. The determination of carrier lifetime as a function of energy of photons that generate the free carriers is discussed.