Search

Resumen del trabajo presentado en el SHIFT2022: Spectral sHapIng For biomedical and energy applicaTions, celebrado en Tenerife (España), del 10 al 14 de octubre de 2022, Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high power conversion efficiency (＞23%) and low-cost fabrication. Directions to further improve these solar cells include strategies to enhance their stability and their efficiency by modifying either the perovskite absorber layer or the electron/hole transport layer. For example, the transparent electron transport layer (ETL) can be an important tuning knob influencing the charge extraction, [1] light harvesting, [2] and stability [3] in these solar cells, or the use of up-conversion nanoparticles to get better performance in the near IR part of the visible spectrum. [4] Here we present two strategies based on nanostructuration, first a fundamental study of upconversion fluorescence enhancement effects near Au nanodisks by scanning near-field optical microscopy and second the effects of a nanocolumnar TiO2 layer on the performance and the stability of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite solar cells. For the first case, the enhancement and localization of light near the metallic structures are directly visualized by using a single Er/Yb-codoped fluorescent nanocrystal glued at the end of a sharp scanning tip. [5] For the second we find that, compared to devices with planar TiO2 ETLs, the TiO2 nanocolumns can significantly enhance the power conversion efficiency of the perovskite solar cells by 17 % and prolong their shelf life. By analyzing the optical properties, solar cells characteristics, as well as transport/recombination properties by impedance spectroscopy, we observed light-trapping and reduced carrier recombination in solar cells associated with the use of TiO2 nanocolumn arrays. [6]

Resumen del trabajo presentado en la Conferencia Española de Nanofotónica (CEN2021), celebrada de forma virtual del 20 al 22 de septiembre de 2021, Organic-inorganic hybrid perovskite solar cells have attracted much attention due to their high power conversion efficiency (¿23%) and low-cost fabrication. Directions to further improve these solar cells include strategies to enhance their stability and their efficiency by modifying either the perovskite absorber layer or the electron/hole transport layer. For example, the transparent electron transport layer (ETL) can be an important tuning knob influencing the charge extraction, [1] light harvesting, [2] and stability [3] in these solar cells, or the use of up-conversion nanoparticles to get better performance in the near IR part of the visible spectrum. [4] Here we present two strategies based on nanostructuration, first a fundamental study of upconversion fluorescence enhancement effects near Au nanodisks by scanning near-field optical microscopy and second the effects of a nanocolumnar TiO2 layer on the performance and the stability of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 perovskite solar cells. For the first case, the enhancement and localization of light near the metallic structures are directly visualized by using a single Er/Yb-codoped fluorescent nanocrystal glued at the end of a sharp scanning tip. [5] For the second we find that, compared to devices with planar TiO2 ETLs, the TiO2 nanocolumns can significantly enhance the power conversion efficiency of the perovskite solar cells by 17 % and prolong their shelf life. By analyzing the optical properties, solar cells characteristics, as well as transport/recombination properties by impedance spectroscopy, we observed light-trapping and reduced carrier recombination in solar cells associated with the use of TiO2 nanocolumn arrays. [6] References: [1] S.S. Mali, et al., Chemistry of Materials 27, 1541 (2015). [2] C. Liu, et al., Journal of Materials Chemistry A 5, 15970 (2017). [3] M. Salado, et al., Nano Energy 35, 215 (2017) [4] M. Bauch et al., Plasmonics 9, 781 (2014) [5] L. Aigouy, et al., Nanoscale 11, 10365 (2019) [6] Z. Hu, et al., ACS Appl. Mater. Interfaces 12, 5979 (2020)

Trabajo presentado en el MRS Fall Meeting, celebrado en Boston, Massachusetts (Estados Unidos), del 1 al 6 de diciembre de 2019, Strategies for controlling and enhancing the fluorescence of molecules and nanocrystals have been the subject of intense research in the past decades [1-3]. This trend is motivated by the need to develop new highly sensitive biosensors, and by the possibility to improve optoelectronic devices like light emitting diodes and solar cells. Here, we present a study of upconversion fluorescence enhancement effects near Au nanodisks by scanning near-field optical microscopy. The enhancement and localization of light near the metallic structures are directly visualized by using a single Er/Yb-codoped fluorescent nanocrystal [4,5] glued at the end of a sharp scanning tip. Excitation was achieved in a transmission mode by a linearly polarized laser diode (l= 975 nm) focused in the tip-sample region. Fluorescence was detected in the visible range after the absorption of two photons by up-conversion. In general, the fluorescence enhancement pattern presents two lobes aligned in the direction of the incident polarization direction, but the intensity amount and the details of the enhancement distribution strongly depend on the nanodisk size. The observed patterns are in good agreement with the near-field maps calculated by finite-difference time-domain method, both in two and three dimensions above the structures. The relationship between the far-field optical response of the nanostructures and the achieved enhancement is also analyzed. [6]

Trabajo presentado en la Conferencia Española de Nanofotonica (CEN2018), celebrada en Donostia-San Sebastian (España), el 3 al 5 de octubre de 2018, Strategies for controlling and enhancing the fluorescence of molecules and nanocrystals have been the subject of intense research in the past decades. This trend is motivated by the need to develop new highly sensitive biosensors, and by the possibility to improve optoelectronic devices like light emitting diodes and solar cells. Here, we present a study of upconversion fluorescence enhancement effects near Au nanodisks by scanning near-field optical microscopy. The enhancement and localization of light near the metallic structures are directly visualized by using a single Er/Yb-codoped fluorescent nanocrystal glued at the end of a sharp scanning tip. Excitation was achieved in a transmission mode by a linearly polarized laser diode (lambda= 975 nm) focused in the tip-sample region. Fluorescence was detected in the visible range after the absorption of two photons by up-conversion. In general, the fluorescence enhancement pattern presents two lobes aligned in the direction of the incident polarization direction, but the intensity amount and the details of the enhancement distribution strongly depend on the nanodisk size. The observed patterns are in good agreement with the near-field maps calculated by finite-difference time-domain method, both in two and three dimensions above the structures. The relationship between the far-field optical response of the nanostructures and the achieved enhancement is also analyzed.

International audience; An original simple technique of ceramic synthesis using soft chemistry route with nanopowders is demonstrated with Yb:CaF 2. We present the first laser operation with these Yb:CaF 2 ceramics, which represents a breakthrough for laser ceramics.

International audience; The design, synthesis and characterization of magnetic-luminescent nanoparticles is now more and more studied since the last decade. However, optimizing the design of such materials requires a deep understanding of their physico-chemical properties. In this paper are reported extended investigations on luminescent and magnetic [Mo6Br14-γ-Fe2O3]@SiO2 nanoparticles prepared by a colloid-water-in-oil microemulsion technique. The Cs2[Mo6Br14] cluster compound is used as red-NIR phosphor and is prepared by solid state chemistry. We bring here new insights into the structure of such Nps and its interplay with their optical or magnetic properties.