arXiv subjects

Maiara Mitiko Taniguchi

Publications and source records attributed to Maiara Mitiko Taniguchi.

3 recordsLinked to original sources

arXiv2020

The role of Ce$^{3+}$/Ce$^{4+}$ in the spectroscopic properties of cerium oxide doped zinc-tellurite glasses prepared under air

Emerging technologies are demanding innovative properties of glasses. In this work, Cerium Oxide is used as a dopant in Zinc-Tellurite samples and its effects on the properties of the glass are investigated. Thermal analysis and x-ray diffraction confirmed the amorphous nature of all samples. The bivalent nature of Cerium is investigated spectroscopically and a strong redshift induced by the dopant is attributed to charge transfers O$^{2-}{\rightarrow}$Ce$^{4+}$, while the 4f-5d transition of Ce$^{3+}$ could not be identified in absorption or luminescence measurements. Yellow/red (570/650 nm) emission under 405/450 nm pumping were observed and are originated from Te$^{4+}$ ions, which absorbs light in the UV/blue region of the spectrum. The incorporation of some Cerium Oxide enhanced the visible luminescence, though we found no evidence that Cerium ions play some role in the radiative process. The luminescence is enhanced though due changes in the glass network induced by the dopant.

cond-mat.mtrl-sci↗

arXiv2020

Glass engineering to enhance Si solar cells: a case study of Pr$^{3+}$-Yb$^{3+}$ codoped tellurite-tungstate as spectral converter

Spectral converters are known to increase photovoltaic energy conversion by minimizing losses due to fundamental non-absorption and thermalization processes, and have been suggested to surpass the Shockley-Queisser efficiency limit in single junction solar cells. Here we present a detailed spectroscopic study of photoluminescence in tellurite-tungstate glasses doped and codoped with $Pr^{3+}-Yb^{3+}$ and $Ag$ nanoparticles. The energy transfer mechanisms between $Pr^{3+}$ and $Yb^{3+}$ are discussed based on the near infrared emission under excitation at $442$ nm and on the upconversion emission under excitation at $980$ nm. Fluorescence quenching of $^2 F_{5/2}$ level of $Yb^{3+}$ is observed by increasing the concentration of $Pr^{3+}$, as well as by the addition of $Ag$ nanoparticles. In addition, a discussion on the potential of this glass to increase energy production in spectral converters is presented. The results suggest that the few undesirable energy transfer processes occurring in this material are difficult to be controlled or eliminated properly, resulting in intrinsic losses. This discussion is extended to the potential of glass science to enhance energy production in solar cells, showing that newer designs such as bifacial cells may facilitate the exploration of glasses other than soda-lime for mass production of solar cells. The focus on extending the lifespan by reducing UV induced degradation seems to be a more effective approach than the development of spectral converters for Si solar cells.

cond-mat.mtrl-sci↗

arXiv2018

On the prospects of enhance glass based devices with silver nanoparticles: the case of Pr3+ doped tellurite-tungstate glasses

The development of enhanced optical devices relies on key materials properties. In this context, researchers have investigated the effects of metal nanoparticles incorporation in active rare-earth materials. Here, we discuss the effects of Silver nitrate addition 0.5%, 1.0% and 2.0% mol%) into a Pr3+ doped tellurite-tungstate glasses (TWNN) formed by the conventional melt-quenching technique. The XRD curves confirmed the amorphous structural nature of TWNN glasses. The FTIR spectra identified the presence of different vibrational groups. DSC curves verified the increase around 70 oC for thermal stability with silver addition. Absorption spectra observed surface plasmon resonance (SPR) band around 500 nm. Luminescence measures shows enhanced and quenching for Pr3+ transitions under the 473 nm excitation. The band around 480-520 nm are more affected by SPR band by quenching, and the bands around 575-675 nm are luminescence emission increased due to the presence of silver nanoparticles. In addition, lifetime decays as a function of heat treatment time, has also been verified. The Ag enhances the lifetime regarding the samples annealed by 20 hours and as the Ag concentration increases, the lifetime stretches as well. The present results shows that Pr3+-Ag codoped TWNN glass lead to some remarkable improvement, verified in properties such as lifetime constants or emissions intensities and is a promising candidate for photonic devices.

cond-mat.mtrl-sci↗