Photoluminescence and Fourier transform infrared spectroscopy measured at room temperature produce strong evidence that nanosized silicon (nc-Si) grains embedded in hydrogenated protocrystalline silicon (i-pc-Si:H) multilayers. Thus, we propose the structure of the i-pc-Si:H multilayer possessing isolated nc-Si grains and their wrapping layers with a high hydrogen concentration embedded in highly hydrogen-diluted sublayers. The isolated nc-Si grains may act as radiative recombination centers of photoexcited carriers, and hence suppress the photocreation of dangling bonds caused by the nonradiative recombination in amorphous silicon matrix. Because of the repeatedly layered structure, the i-pc-Si:H multilayers have a fast light-induced metastability with a low degradation. (c) 2006 American Institute of Physics.