Molecular‐Like Ag Clusters and Eu³⁺ Co‐Sensitized Efficient Broadband Spectral Modification with Enhanced Yb³⁺ Emission

Abstract

AgNO 3 /EuF 3 /YbF 3 tri-doped oxyfluoride glass was prepared by a melt-quenching method, in which a high-efficient broadband spectral modification can be realized due to the simultaneous energy-transfer processes of Eu 3+ ?Yb 3+ , molecular-like Ag (ML-Ag) clusters?Yb 3+ , and ML-Ag clusters? Eu 3+ ?Yb 3+ . The spectral measurements indicated that besides the F-center brought by the fluorides, the formation of the ML-Ag clusters and the evolution of silver species within the glass matrix were also closely related to the introduction of Eu 3+ and Yb 3+ ions and which in return greatly affected the luminescence properties of these rare-earth ions. As the UVvisible irradiation in the wavelength region of 250-600 nm can be efficiently converted into near-infrared emission around 1000 nm in the AgNO 3 /EuF 3 /YbF 3 tri-doped glass, which thus has promising application in enhancing the photovoltaic conversion efficiency of the silicon solar cell.

Luminescence properties and tunable emission of Ag NCs in oxyfluoride glass through REF3 (RE = Y, La and Gd) doping

“…It should be noticed that the doping of 0.3 mol% REF 3 (RE = Y, La, and Gd) also introduced extra fluoride content into the glass composition, which can promote the growth of Ag NCs due to the formation of more F‐center clusters that acted as the favorable nucleation centers . On the other hand, it has been proved that the formation of Ag NCs requires the reduction in Ag + ions . Ionic electronegativity is a chemical property that describes the tendency of an ion to attract electrons or electron density towards itself.…”

“…Further research indicated that the tunable light emission can be realized in the EuF 3 /AgNO 3 co‐doped oxyfluoride glasses by adjusting the glass composition . Another promising application is the spectral down‐shifting for the enhancement of solar cell photovoltaic conversion efficiency, which was reported in the AgNO 3 /YbF 3 co‐doped or EuF 3 /AgNO 3 /YbF 3 tri‐doped oxyfluoride glasses, very strong infrared emission can be achieved through the direct energy from Ag NCs to Yb 3+ ions, or multiple energy transfer processes of Eu 3+ →Yb 3+ , Ag NCs→Yb 3+ , and Ag NCs→Eu 3+ →Yb 3+ …”

“…Previous investigation indicated that many factors may affect the evaluation of Ag species (including Ag + ions, Ag NCs and AgNPs) and the size distribution of Ag NCs in glass, such as the silver doping concentration, the fluoride content and monovalence cation (Na + , K + ) that constitutes the host composition, and the afterward heat treatment . Besides, it was reported that the doping of luminescent RE ions with alternative valance, such as Eu 3+ , Sm 3+ and Yb 3+ , can obviously promote the formation of Ag NCs and thus modified their emission wavelength …”

“…6 Another promising application is the spectral down-shifting for the enhancement of solar cell photovoltaic conversion efficiency, which was reported in the AgNO 3 /YbF 3 co-doped or EuF 3 /AgNO 3 /YbF 3 tri-doped oxyfluoride glasses, very strong infrared emission can be achieved through the direct energy from Ag NCs to Yb 3+ ions, or multiple energy transfer processes of Eu 3+ ?Yb 3+ , Ag NCs?Yb 3+ , and Ag NCs?Eu 3+ ?Yb 3+ . 12,13 It has been well-established that the resonance energy transfer requires the overlap of the photoluminescence (PL) spectra of the sensitizer and the photoluminescence-excitation (PLE) spectra of the activator. 14,15 Therefore, it is of great importance to precisely control the size distribution of Ag NCs to obtain high-efficient emission at selected wavelength region to achieve efficient energy transfer to various RE ions with different excitation bands.…”

“…6,[16][17][18] Besides, it was reported that the doping of luminescent RE ions with alternative valance, such as Eu 3+ , Sm 3+ and Yb 3+ , can obviously promote the formation of Ag NCs and thus modified their emission wavelength. 12,16,19 In this research, the luminescence properties of Ag NCs were systematically discussed and LaF 3 , YF 3 , and GdF 3 were selected as dopants to control the size distribution of Ag NCs. As the La 3+ , Y 3+ , and Gd 3+ ions have neither absorption nor emission at visible region, the influence of energy transfer between Ag NCs and RE ions on the PL spectral profile of Ag NCs can be avoided.…”