In silicon solar cells, carriers are generated under illumination of laser, and excess minority carriers emit infrared radiation via a radiative recombination process. A model for minority carrier density in a pn junction induced by modulated laser was developed based on 1D carrier transport equation of semiconductor. The influences of carrier lifetime, diffusion coefficient, surface recombination rate, and photovoltage on radiation recombination, thus on infrared radiation were investigated. The laser-induced photocarrier radiometry signal was monitored using an InGaAs detector (0.9~1.7μm). The amplitude and phase of infrared radiation were obtained by a digital lock-in amplifier. Carrier transport parameters of m-Si solar cell were obtained by frequency-scanning experiments.