Organic luminescent ink (L-ink) is disclosed for use in printing thin films of organic luminescent material. The L-ink is particularly useful in fabricating organic optoelectronic devices, e.g. organic luminescent devices. The L-ink contains at least one organic luminescent material mixed with a solvent and other functional additives to provide the necessary optical, electronic and morphological properties for light-emitting devices (LEDs). The additives play an important role either for enhanced thin film printing or for better performance of the optoelectronic device. The functional additives may be chemically bound to the luminescent compounds or polymers. Luminescent organic compounds, oligomers, or polymers with relatively low solution viscosity, good thin film formability, and good charge transporting properties, are preferred. The L-inks can be cross-linked under certain conditions to enhance thin film properties. The L-ink can be used in various printing methods, such as screen printing, stamp printing, and preferably ink-jet printing (including bubble-jet printing).