This article studies theoretically and experimentally the recombination at the amorphous/crystalline silicon interface of a heterojunction with intrinsic thin layer (HIT) structure without metallization. We propose a physical model to calculate the interface recombination rate under illumination. This model calculates the effective lifetime teff as a function of the average excess minority carrier concentration¿¿n¿. In order to test the model, we prepared a set of HIT structures. The dependence of teff vs ¿¿n¿ of the samples is measured using the quasi-steady-state photoconductance technique. By fitting our model to the experimental data, we determine the a-Si:H/c-Siinterface parameters and the doping density of the amorphous layer.