ABSTRACT
In this era of technology, there is a crucial demand for the development of a highly efficient light source and hence, there is a serious need to design energy-saving LED phosphor which can absorb excitation energy in the UV region and exhibit desired emission in the visible region. Rare-earths, specifically lanthanide series elements, play a very important role in phosphors owing to their numerous characteristics such as high control over the color emission, exhibiting strong absorption due to optical transitions within the f-manifold, and excellent ability to capture energy photons due to high atomic number as well as high density. In this chapter, we focus on the fundamental spectroscopic properties and electronic structure of rare-earth elements. The selection rule which describes the allowed or forbidden possibility of spectral transition with a discussion on light absorption and emission mechanism will be elaborated briefly. Special attention is devoted to the optical properties and performance of rare-earth-activated energy-saving LED phosphor. In particular, the phenomenon related to tuning the luminescence via energy transfer and its role in the host matrix for LED phosphors will be discussed.
