Title: Applications of Mn4+ ions in red phosphors for white LEDs
Speaker: Prof. Mikhail G. Brik, University of Tartu
Venue: Meeting Room 502, Science Park Building No.1, Northern Area, Wushan Campus
Time: December 13, Friday, 15:00-17:00
Great attention is being paid now to the development of new and improvement of already existing Mn4+-based red phosphors. These materials became a very important part of the white light emitting diodes (LEDs). If the red emission that is due to the 2E→4A2 emission of the Mn4+ ions is at about 620 nm, then the color correlated temperature of the white LEDs is lowered (warm white light will be emitted) and color rendering index will be increased. All this will improve the characteristics of the white LEDs.
The main emphasis in this presentation will be placed on the recently found relations between the emission properties of various fluoride- and oxide-based red phosphors doped with the Mn4+ ions with the hosts crystal structure and nature of the ligands. The local symmetry of the crystallographic site occupied by the Mn4+ ions is highlighted as a key factor that determines emission features of the impurity. In this respect, it is essential to remove the inversion center of the crystallographic site occupied by the Mn4+ ions. This can be achieved by different methods, which are discussed in our papers in detail. Quantitative analysis of the Mn4+ energy levels in a number of hosts is also presented.
Mikhail G. Brik received his PhD from Kuban State University (Russia) in 1995 and his DSc (habilitation) from the Institute of Physics, Polish Academy of Sciences (Poland) in 2012. Since 2007 he is a professor at the Institute of Physics, University of Tartu, Estonia. Before that, he worked at Kyoto University (Japan) from 2003 to 2007, Weizmann Institute of Science (Israel) in 2002, Asmara University (Eritrea) from 2000 to 2001, and Kuban State University from 1995 to 2000. He is also a distinguished visiting professor at Chongqing University of Posts and Telecommunications (China) and Professor at Jan Długosz University (Poland). Since 2015 he serves as one of the editors of Optical Materials (Elsevier). Prof. Brik’s scientific interests cover theoretical spectroscopy of transition metal and rare earth ions in optical materials, crystal field theory, and ab initio calculations of the physical properties of pure and doped functional compounds. He is a coeditor of two books and author of 12 book chapters and about 390 papers in international journals. According to Google Scholar (November 2019), he has more than 7600 citations with h index 42. He received the Dragomir Hurmuzescu Award of Romanian Academy in 2006 and the State Prize of the Republic of Estonia in the field of exact sciences in 2013. In 2018 he received the state professor title from the President of Poland.
Announced by the School of Materials Science and Engineering