The time-dependent formation of one-dimensional (1D) photovoltaic solitons under open-circuit conditions are researched theoretically. The differential equations of profile of bright and dark photovoltaic solitons are obtained by the numerical method. The effects of the background light on the photovoltaic solitons and their width full-width at half maximum (FWHM) are studied. The results show that applying the background light results in shorting the formation time of photovoltaic solitons, and the ratio of formation time without the background light to that with the background light quals the ratio of the intensity of background light to that of dark irradiation. The higher the ratio of soliton peak intensity to the sum of background light and dark irradiation intensity, the shorter the time of the FWHM of photovoltaic soliton reacheing steady-state.