the present invention discloses a simple , low cost method to fabricate light emitting source using luminescent colloid nanoparticles . it uses monodispersed colloid light emitting nanoparticles of oxides , semiconductors , and polymers to fabricate high quality , narrow bandwidth light emitting source . the colloid particles can be dispersed homogeneously in liquid that can be coated easily on a substrate using a simple coating method such as spray , dip coating or spin coating . there is no restriction on the size or shape of the substrate . therefore , a low cost , large area , high efficiency and reproducible light emitting source can be made easily .