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In memoriam: Victor Tikhomirov

In memoriam
in honor of Victor Tikhomirov
26-12-1961 St.-Petersburg – 09-01-2014 Leuven
Senior Postdoctoral Researcher
Department of Physics and Astronomy, KU Leuven



Enjoying the sun’s light

The feeling of summer is for most people an every year returning blessing, the sun shining on our skin, the smell of sea and beach, and the much needed relaxation during the holiday season. Few things are experienced this positive as when the sun stands high in a clear sky. Even physicists enjoy the sun, some more than others, and some even for a completely different reason... When Dr. Tikhomirov joined our research team in Leuven, he did bring with him a fascination of sunlight, in all of its colors/wavelengths. As so typical for scientists, his main concern was somewhat different, i.e. his main question was “how to harvest all this sunlight most efficiently by generating energy from sunlight”.

His work originated from his early days as a Ph.D. student in Russia, and was irrevocably connected with introducing energy transferring elements in glasses, which could be used as coating for conventional solar cells. The efficiency of solar cells is among other parameters quite strongly correlated with the energy difference between the electrons which contribute to conduction and the bound valence electrons (i.e. bandgap). Only light of the “right” energy can create electron-hole pairs, which are essential for the production of electricity by solar cells. As such, from all the abundant sunlight, only a small fraction is actually suited to generate energy within a solar cell.

Dr. Tikhomirov’s main concern was to find the ways which would allow using a broader spectrum of light to be used for energy generation. This process takes advantage of a process called optoelectronic conversion, and besides for solar cells, it can be used for many different applications like luminescent lamps and flexible screens. Both down and up conversion can be used, one allowing to combine photons (light particles) to excite a valence band electron, the other to share one photon to excite more than one valence electron.

To achieve this, Dr. Tikhomirov used, among other tricks, rare earth dopants and Ag nanoclusters doping in his glasses; a process which he optimized by seeking the right dopant concentrations, glass components and annealing/melting treatments. Some of his most successful studies were on “the fabrication and characterization of nanoscale, Er3+-doped, ultra transparent oxy-fluoride glass ceramics” (2002), “Erbium-doped tellurite glasses with high quantum efficiency and broadband stimulated emission cross section at 1.5 µm” (2003), and “Towards broad range and highly efficient down-conversion of solar spectrum by Er3+-Yb3+ co-doped nano-structured glass-ceramics” (2010). More recently, “Ag nanocluster functionalized glasses for efficient photonic conversion in light sources, solar cells and flexible screen monitors” (2013) reviewed for the scientific community, this new and promising track, to achieve the final harvesting of the sun’s energy. In the figure, you can see a typical luminescent spectrum, several luminescent pieces of glass, and a conversion scheme, as published in Nanoscale, 2013, 5, 10065–10075, where this figure ornamented the cover page.

With the departure of Dr. Tikhomirov from this world, the scientific community lost a fundamental scientist with great interest for applications of considerable societal importance.

We publish this in memoriam note in his honor.

By Mikhail Shestakov, Alexandre Kuznetsov, Johan Vanacken, Liviu Chibotaru and Victor Moshchalkov.