Enrichi Francesco, Cattaruzza Elti, Ferrari Maurizio, Gonella Francesco, Ottini Riccardo, Riello Pietro, Righini Giancarlo C, Enrico Trave, Vomiero Alberto, Zur Lidia
Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", Roma 00184, Italy.
Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, Luleå 97187, Sweden.
Micromachines (Basel). 2018 Jul 31;9(8):380. doi: 10.3390/mi9080380.
Rare earth doped materials play a very important role in the development of many photonic devices, such as optical amplifiers and lasers, frequency converters, solar concentrators, up to quantum information storage devices. Among the rare earth ions, ytterbium is certainly one of the most frequently investigated and employed. The absorption and emission properties of Yb ions are related to transitions between the two energy levels ²F (ground state) and ²F (excited state), involving photon energies around 1.26 eV (980 nm). Therefore, Yb cannot directly absorb UV or visible light, and it is often used in combination with other rare earth ions like Pr, Tm, and Tb, which act as energy transfer centres. Nevertheless, even in those co-doped materials, the absorption bandwidth can be limited, and the cross section is small. In this paper, we report a broadband and efficient energy transfer process between Ag dimers/multimers and Yb ions, which results in a strong PL emission around 980 nm under UV light excitation. Silica-zirconia (70% SiO₂-30% ZrO₂) glass-ceramic films doped by 4 mol.% Yb ions and an additional 5 mol.% of Na₂O were prepared by sol-gel synthesis followed by a thermal annealing at 1000 °C. Ag introduction was then obtained by ion-exchange in a molten salt bath and the samples were subsequently annealed in air at 430 °C to induce the migration and aggregation of the metal. The structural, compositional, and optical properties were investigated, providing evidence for efficient broadband sensitization of the rare earth ions by energy transfer from Ag dimers/multimers, which could have important applications in different fields, such as PV solar cells and light-emitting near-infrared (NIR) devices.
稀土掺杂材料在许多光子器件的发展中起着非常重要的作用，如光放大器、激光器、频率转换器、太阳能聚光器，乃至量子信息存储设备。在稀土离子中，镱无疑是研究和应用最为频繁的离子之一。镱离子的吸收和发射特性与两个能级²F（基态）和²F（激发态）之间的跃迁有关，涉及的光子能量约为1.26电子伏特（980纳米）。因此，镱不能直接吸收紫外线或可见光，它常与其他稀土离子如镨、铥和铽结合使用，这些离子充当能量转移中心。然而，即使在那些共掺杂材料中，吸收带宽也可能受到限制，且截面较小。在本文中，我们报道了银二聚体/多聚体与镱离子之间的宽带高效能量转移过程，在紫外光激发下，该过程会在980纳米附近产生强烈的光致发光发射。通过溶胶 - 凝胶合成法制备了掺杂4摩尔%镱离子和额外5摩尔%氧化钠的二氧化硅 - 氧化锆（70% SiO₂ - 30% ZrO₂）玻璃陶瓷薄膜，随后在1000°C下进行热退火。然后通过在熔盐浴中进行离子交换引入银，随后将样品在空气中于430°C退火以诱导金属的迁移和聚集。对其结构、成分和光学性质进行了研究，为通过银二聚体/多聚体的能量转移对稀土离子进行高效宽带敏化提供了证据，这在光伏太阳能电池和近红外发光（NIR）器件等不同领域可能具有重要应用。
