Efficient near-infrared quantum cutting by cooperative energy transfer in Bi3TeBO9:Nd3+ phosphors

A Majchrowski,M Nowicki,K M Kosyl,D Kasprowicz,T Zhezhera,P Gluchowski,M Chrunik

doi:10.1007/s10853-021-06642-2

Abstract

An efficient near-infrared quantum cutting process by cooperative down-conversion of active Bi3+ and Nd3+ ions was demonstrated in Bi3TeBO9:Nd3+ phosphors. In particular, the near-infrared emission of Nd3+ ions enhanced by Bi3+ ions of a series of novel Bi3TeBO9:Nd3+ microcrystalline powders doped with Nd3+ ions in various concentrations was investigated. In order to investigate the luminescent properties of BTBO:Nd3+ powders, the excitation and emission spectra and the fluorescence decay time were measured and analyzed. In particular, the emission of Bi3TeBO9:Nd3+ at 890 and 1064 nm was excited at 327 nm (via energy transfer from Bi3+ ions) and at 586.4 nm (directly by Nd3+ ions). The highest intensity emission bands in near-infrared were detected in the spectra of Bi3TeBO9:Nd3+ doped with 5.0 and 0.5 at.% of Nd3+ ions upon excitation in ultraviolet and visible spectral range, respectively. The fluorescence decay lifetime monitored at 1064 nm for Bi3TeBO9:Nd3+ powders shows the single- or double-exponential character depending on the concentrations of Nd3+ ions. The possible mechanisms of energy relaxation after excitation Bi3TeBO9:Nd3+ powders in ultraviolet or visible spectral range were discussed. The investigated Bi3TeBO9:Nd3+ phosphors efficiently concentrate the ultraviolet/visible radiation in the near-infrared spectral range and can be potentially used as effective spectral converters.Graphical abstract

Highlights

The efficiency of spectral converters based on rare earth (RE) ions doped crystalline materials is related to the characteristic energy level structures of RE ions, which allows up- and/or down-conversion processes by resonant energy transfer between lanthanide ions [1]
B atoms are surrounded by three O atoms to form the trigonal-planar BO3 groups with uniform B - O bond lengths, while Te6? cations are coordinated by six O atoms with different Te - O bond lengths. (The TeO6 octahedra are slightly deformed from the regular octahedral configuration.) Owing to the size similarity of the ionic radii of the Nd3? and Bi3? ions, in the doped BTBO microcrystals, Bi3? ions can be efficiently substituted by Nd3? ions
The investigated BTBO:Nd3? microcrystalline powders doped with Nd3? ions in various concentrations

Summary

Introduction

The efficiency of spectral converters based on rare earth (RE) ions doped crystalline materials is related to the characteristic energy level structures of RE ions, which allows up- and/or down-conversion processes by resonant energy transfer between lanthanide ions [1]. The photons with energies smaller than Eg are not absorbed and their energy is not used for electrons generation, while the photons with energies higher than Eg are absorbed, but the excess energy is lost due to thermalization of the generated electrons [4] These spectral losses in a single-junction crystalline silicon (c-Si) solar cells limit the efficiency of solar energy conversion into electricity. The high-energy region of the solar spectrum cannot be utilized by conventional c-Si solar cells as silicon has a band gap Eg = 1.12 eV, corresponding to the absorption in the NIR spectral range & 1100 nm [5]. The proposed solution is to convert the high-energy part of the solar spectrum into the low energy NIR region, from which the solar energy can be efficiently absorbed by the c-Si solar cells

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