The vacuum referred binding energy (VRBE) of the single electron in the lowest energy 3d level of Sc 2+ , V 4+ , Cr 5+ , the lowest 4d level of Y 2+ , Zr 3+ , Nb 4+ , Mo 5+ and the lowest 5d level of Ta 4+ , and W 5+ in various compounds are determined by means of the chemical shift model. They will be compared with the VRBE in the already established lowest 3d level of Ti 3+ and the lowest 5d level of Eu 2+ and Ce 3+ . Clear trends with changing charge of the transition metal (TM) cation and with changing principle quantum number n = 3, 4, or 5 of the nd level will be identified. This work will demonstrate that the trends correlate with the VRBE in the free ion nd TM cation level. The acquired knowledge on the VRBE of the electron in the nd TM impurity levels but also on TM based compounds with nd type of conduction band bottom provides new insight in the luminescence properties of TM activated compounds. © 2014 The Electrochemical Society. [DOI: 10.1149/2.0121410jss] All rights reserved.Manuscript submitted May 23, 2014; revised manuscript received July 22, 2014. Published August 7, 2014 We live in a world where energy and resource efficiencies are becoming more and more important. Optimized luminescent materials are required for light emitting diodes of the correct hue, [1][2][3][4] to improve the efficiency of solar cells, [5][6][7] to make longer lasting and brighter "glow in the dark" phosphors, [8][9][10] and for faster, brighter, more proportional scintillators for particle and astro-physics, medical imaging and homeland security, [11][12][13][14] and this is all needed with resources that may be limited by physical availability or global politics. [15][16][17][18] It is neccessary therefore to find improved and/or alternative luminescent materials. The use of ab initio or semi-empirical models to predict the optical properties and electronic structures of luminescent materials are important in aiding this work, see e.g. Refs. 19-22. Such models may be used to identify areas of interest, for instance identifying a promising new combination of host compound and dopant ion. They may also be used in a systematic study of whole families of compounds in order to gain new understanding of the underlying physics, 21,23 or to better understand the performance of an existing luminescent material.The location of lanthanide impurity levels in inorganic compounds has been a subject of interest for many years. In 2003 Dorenbos introduced a semi-empirical model to determine the electron binding energies in the 4f and 5d levels of lanthanides relative to the energy at the top of the host valence band in inorganic compounds. 25 Figure 2 summarizes the notation used to describe the optical transitions of relevance in this article. Ti 4+ is used in Fig. 2 to represent the transition metals while Ce 3+ , Eu 3+ and Pr 3+ are used to represent the lanthanides. Energies are expressed relative to the vacuum level (E vac ) which is the energy of an electron at rest in the vacuum. Lanthanide spectroscopy, combined with the chemi...
