SV Kuznetsov, AS Nizamutdinov, MN Mayakova…
Abstract
The forecast for the development of renewable energy [1], conducted by Fraunhofer ISE, showed that by 2030, humanity will reach the terawatt power generation capacity through photovoltaic devices. About 95 percent of this power will be generated by silicon solar panels. The cost of generating 1 kilowatt hour (kWh) of energy will be no higher than the cost of generating energy from fossils and nuclear power. One of the most significant drawbacks of Si-based solar cells is the low efficiency of power generation due to the limited range of high spectral susceptibility of crystalline silicon to sunlight. There are various options to increase the efficiency [2–8], including additional layers based on up-conversion (UC) [6,7] and down-conversion [8] luminophores. These methods result in energy transfer from non-sensitive regions of the spectrum to crystalline silicon photosensitive range. The most efficient UC material excited at 980 nm is β-NaYF4:21.4%Yb:2.2%Er with a reported photoluminescence quantum yield (PLQY) 10.5 % at pump power density P=35 W/cm2 [9]. Other efficient UC materials described in the literature include BaY2ZnO5:7%Yb:3%Er with PLQY=5 % at P=2.2 W/cm2 [10], La2O2S:9%Yb:1%Er with PLQY=5.8 % at P=13 W/cm2 [11] and SrF2:Yb(2 mol.%):Er(2 mol%) with PLQY=2.8 % at 10 W/cm2 [7]. The phenomenon of quantum cutting is one of the down-conversion mechanisms, which allows one to transform the blue pump radiation to near infrared with an efficiency of more than 100 %. It was previously shown, that one of the most promising from the point of view of high quantum energy transfer efficiency is the ytterbium-praseodymium doping pair [12–17]. Previously, we studied solid solutions based on calcium fluoride and strontium fluoride doped with praseodymium and ytterbium [18,19]. The best result was achieved for a solid solution based on SrF2, which demonstrated an energy transfer coefficient of more than 100 % and a quantum yield of 1.1 % [18]. Usually, the luminescence efficiency increases with the transition to heavier matrices and with reduced symmetry. In this connection, it was logical to proceed to the study of fluorite solid solutions based on barium fluoride. It was previously shown that it was impossible to synthesize single-phase solid solutions Ba1−xRxF2+x (R – rare earth elements) by co-precipitation technique [20–22], since two-phase samples were synthesized. It is possible to synthesize Ba1−xRxF2+x solid solutions by high temperature melting technique, while fluorite-related trigonal Synthesis and down-conversion luminescence of Ba4Y3F17:Yb:Pr solid solutions for photonics 191 distorted Ba4Y3F17 single-phases are synthesized from aqueous solutions [20–23]. The aim of this work was to study the synthesis and spectral-luminescent characteristics of Ba4Y3F17 solid solutions.
Luminescence spectra of Ba4Y3F17:Pr(0.1 %):Yb(10.00 %) (1) and Ba4Y3F17:Pr(0.1 %):Yb(15.00 %) (2) powder samples excited by 445 nm CW laser light. The sign (*) indicates the second order observation of excitation light
Diffusion reflection spectrum of Ba4Y3F17:Pr(0.1 %):Yb(1.0 %) powder sample. The inset shows the magnified visible spectral range reflection
… Diffuse reflection spectra were recorded by a Thorlabs IS200 integrating sphere and a StellarNet EPP2000 spectrometer equipped with deuterium and halogen lamps … The radiation from the integrating sphere was
