Hendrik C Swart is a B1 NRF rated researcher and currently a senior professor in the Department of Physics at the University of the Free State. Over the past 20 years he has led research in the area of the degradation of phosphors for field emission displays, as well as developing materials for nano solid state lighting. He has been key in the development of processes to synthesise and deposit thin films of various types of semiconductor nano-particles which will enhance the colour, luminescent intensity and lifetime of such displays. He has more than 450 publications in international peer reviewed journals, 100 peer reviewed conference proceedings and editor/author or co-editor/author of 12 book chapters and or books with more than 3460 cited author references and more than 530 national and international conference contributions (authored and co-authored). He has an ISI H-index of 27 (rid=g-2696-2012). He is a reviewer for about 50 international and national professional journals in his field (or in related fields), and a member of the editorial board of the high impact factor journal ‘Critical Reviews in Solid State and Materials Sciences. He is on the editorial boad of Applied Surface Science and one of the newly appointed editors of the Journal of Nano Research. He has received the South African National Science and Technology Forum (NSTF) award in 2009 for research capacity development of students in the niche area of nanophysics. His commitment to the next generation of scientists is also reflected by the awards he received from the Faculty of Natural and Agricultural Sciences at the University of the Free State, South Africa for excellence (2012), research (2014), mentorship (2008) and for academic entrepreneurship (2009). The International Association of Advanced Materials (IAAM) honored him with the the prestigious IAAM Scientist award for 2014 at the SETCOR International Conference on Smart Materials and Surfaces, Bangkok - Thailand.  He received honorary membership of the Golden Key Association (2012). He was chair of national and international conferences and gave several keynote and invited talks. He has supervised 60 PhD and MSc students successfully in the past with another 17 in progress and has established a National Nano Surface Characterization Facility (NNSCF) containing state of the art surface characterization equipment. Interdisciplinary results obtained with these systems were recently selected for the cover of Federation of European Microbiological Societies (FEMS) Yeast research journal for 2013. A research chair in Solid State Luminescent and Advanced Materials was awarded to him from the South African Research Chairs Initiative (SARChI) at the end of 2012. The main focus of his research group will be the improvement of luminescent materials for applications in Flat Panel Displays and Solar Cells; the development of Organic light emitting diodes (OLED) materials as well as materials for power saving solid state lighting devices.


Phosphor materials for Solid State Lighting and Solar cell applications.

H.C. Swart 

Department of Physics, University of the Free State, Bloemfontein, ZA9300, South Africa 
Email: swarthc@ufs.ac.za

        Luminescent compounds and materials have numerous uses. The emission properties, whether of a fast decay rate fluorescent material or a slow decay rate phosphorescent material, are defined by the chemical composition and the physical structure of the luminescent material. The crystal field that is determined by the environment in the host material in combination with the various dopant ions with the correct valence state can be used to obtain emissions from the Ultra violet (UV) to the infra-red (IR) wavelength ranges. Phosphor materials have been successfully used to improve the efficiency of various applications. Nanoparticles both undoped and doped with different rare earth elements were synthesized by several synthesized techniques. The strong deep level emission (DLE) and near band edge emission could be tuned to cover a wide spectral range.  The strong DLE, covering a wide spectral range of ~375-650 nm, signifies the potential optoelectronics application in the near white LED applications.  The major problem that limits solar cells’ efficiency is their insensitivity to the whole solar spectrum which is the so-called spectral mismatch. Therefore, several mechanisms have been explored based on PL to convert the solar cell spectrum where the spectral response of the solar cell is low to regions where the spectral response of the solar cell is high. Down-conversion, up-conversion and downshifting are some of the mechanisms that may be applied to improve the spectral response. Degradation of the different phosphors during prolonged electron/photon bombardment also played a vital role in their possible applications. Examples of different phosphor materials with different applications such as Solid State Lighting will be shown. 

Keywords: XPS, AES, TOF SIMS, Solid State Lighting.

Acknowledgements
        South African Research Chairs Initiative of the Department of Science and Technology (DST) and the National Research Foundation (NRF) (Grants 88415 and 93214).

References
[1] H.C. Swart, I.M. Nagpure, O.M. Ntwaeaborwa, G.L. Fisher and J.J. Terblans, Optics Express, 20(15) (2012) 17119-17125.
[2] H.C. Swart, J.J. Terblans, O.M. Ntwaeaborwa, R.E. Kroon, E Coetsee, I.M. Nagpure, Vijay Kumar, Vinod Kumar and Vinay Kumar, Surf. Interf. Anal., 46(10-11) (2014) 1105-1109.



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