Abstract
The optical photoluminescent (PL) emission of Yb3+ ions in the near infrared (NIR) spectral region at about 950–1100 nm has many potential applications, from photovoltaics to lasers and visual devices. However, due to their simple energy-level structure, Yb3+ ions cannot directly absorb UV or visible light, putting serious limits on their use as light emitters. In this paper we describe a broadband and efficient strategy for sensitizing Yb3+ ions by Ag codoping, resulting in a strong 980 nm PL emission under UV and violet-blue light excitation. Yb-doped silica–zirconia–soda glass–ceramic films were synthesized by sol-gel and dip-coating, followed by annealing at 1000 °C. Ag was then introduced by ion-exchange in a molten salt bath for 1 h at 350 °C. Different post-exchange annealing temperatures for 1 h in air at 380 °C and 430 °C were compared to investigate the possibility of migration/aggregation of the metal ions. Studies of composition showed about 1–2 wt% Ag in the exchanged samples, not modified by annealing. Structural analysis reported the stabilization of cubic zirconia by Yb-doping. Optical measurements showed that, in particular for the highest annealing temperature of 430 °C, the potential improvement of the material’s quality, which would increase the PL emission, is less relevant than Ag-aggregation, which decreases the sensitizers number, resulting in a net reduction of the PL intensity. However, all the Ag-exchanged samples showed a broadband Yb3+ sensitization by energy transfer from Ag aggregates, clearly attested by a broad photoluminescence excitation spectra after Ag-exchange, paving the way for applications in various fields, such as solar cells and NIR-emitting devices.
Highlights
Rare earth ions (RE3+ ) have many optical applications due to their unique spectral properties, in relation to the features of their electronic energy levels, covering UV, visible and IR [1]
Yb3+ ions provide near infrared (NIR)
The film composition was confirmed by Rutherford backscattering spectrometry (RBS) analysis in agreement with the nominal values for
Summary
Rare earth ions (RE3+ ) have many optical applications due to their unique spectral properties, in relation to the features of their electronic energy levels, covering UV, visible and IR [1]. This makes them excellent for lighting [2,3,4], displays [5], biosensing [6,7,8], optical amplification2 [9], Appl. Structuralcontrolled and optical were combined forannealing retrieving role andCompositional, nature of Ag-aggregates by Agmeasurements followed by at Ag different temperatures, their interaction with Yb ions for obtaining efficient sensitization and by annealing at different temperatures, and their interaction with Yb3+ ions for obtaining efficient photoluminescence boosting
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