In the present paper, the experimental results on Langmuir-Blodgett (LB) modification and photosensitization of hydrogenated amorphous silicon (a-Si:H) with some dipyridine derivatives containing the photoactive groups are reported. The dipyridine derivatives were assembled on the surface of the a-Si:H film by a LB technique. The photovoltaic properties of the LB-modified a-Si:H films as well as the processes of the interfacial charge transfer were systematically investigated by steady-state and time-resolved surface photovoltage spectroscopy. The results reveal that the LB-modified a-Si:H films yield a stable photovoltage much higher in magnitude than the unmodified one, Based on the measurements, a model is proposed for the illustration of the observations. The effects of LB modification of a-Si:H films on the photovoltaic behaviors are due to the chemical attachment and incorporation of the photoactive compounds involved in photoinduced charge separation.