Surface-passivated photoluminescent carbon dots (CDs) were prepared via a facile one-step pyrolysis of poly(acrylic acid) (PAA) in the presence of glycerol. In the formation process of CDs, glycerol not only acts as solvent, but also promotes the carbonization of PAA (carbon source) and passivates the surface of CDs. The as-prepared CDs can emit bright. white fluorescence under ultraviolet (UV) illumination. The structure and optical properties of the CDs were thoroughly investigated. The CDs show excellent solubility in water and high photoluminescence stability in UV-radiation, salty, oxidic, or reductive environments, suggesting their great promise as white-light-emitting materials. For their practical applications, a white light-emitting diode (LED) with CDs as white-light converters was demonstrated. Moreover, a backlight with use of CDs as coatings was successfully constructed for the first time. This research would offer a promising new way to obtain white fluorescent CDs and suggests their strong potential for solid-state lighting systems.