In this paper recent advances in the development of efficient light conversion molecular devices (LCMD) based on lanthanide complexes are reviewed, with emphasis on the work of our group. We have adopted a strategy based upon both theoretical and experimental (synthesis and methodological) investigations. The theoretical aspects are described in terms of the well known theory of 4f–4f transitions and a recently developed model of intramolecular energy transfer processes in lanthanide coordination compounds. The necessary structural data (coordination geometries and electronic structures of the organic parts of the compounds) are obtained from a sparkle model also recently developed. The results lead us to achieve a better understanding of the factors determining the quantum yields and other relevant properties of these complexes, establishing the basis of a framework for the modeling of new complexes which are promising LCMDs. In addition, the fluorinated compounds, which are sufficiently volatile and thermodynamically stable, are candidates for a number of applications. We illustrate their use as LCMDs devices for sensing UV radiation (dosimeter) and as antireflection coatings (ARC) on silicon solar cells with beneficial effects on device performance.