The addition of a variety of additives to a soluble electroluminescent polymer in solution is used to improve the printability and performance of screen printed light-emitting polymer-based devices. Examples of such additives include transparent polymers, gel-retarders, high viscosity liquids, organic and inorganic salts, and oxide nanoparticles. The additives are used to control the viscosity of the electroluminescent polymer ink, to decrease the solvent evaporation rate, and to improve the ink consistency and working time. In addition, these additives can improve the charge injection and power efficiency of light emitting devices manufactured from the screen printable electroluminescent polymer ink.