Upconversion and Anti-Stokes Processes With f and d Ions in Solids

GOTR, UMR 7574-CNRS, 1, Place A-Briand, 92195 Meudon Cedex, France.
Chemical Reviews (Impact Factor: 46.57). 02/2004; 104(1):139-73. DOI: 10.1021/cr020357g
Source: PubMed


The anti-Stokes emissions or upconversion processes, for which emissions was found to exceed excitation energies by 10-100 kT, were presented. The dissolution of nanoparticles (6-8 nm) of Yb-Er- and Yb-Tm doped LuPO 4 as colloids in chloroform solutions was demonstrated. The Nd 3+-Yb3+ codoped YA nanocrystalline cemramics were also studied. It was observed that in thermoluminescence, where traps were emptied by excitation energies of the order of kT, constituted a field of anti-Stokes emission of its own.

Full-text preview

Available from:
  • Source
    • "H 11/2 states, populated by more than two photon processes [44], contribute to the photocurrent of the silicon solar cell. Intense green luminescence due to the "
    [Show abstract] [Hide abstract]
    ABSTRACT: Up-conversion (UC) is a promising approach to utilize sub-band-gap photons for solar cells (SCs). Due to the non-linear nature of UC, the optimal excitation power regimes between the solar cell semiconductor and the UC material correspond to a difference in solar concentration of more than an order of magnitude. This difference can be bridged with integrated optics by concentrating the photons transmitted through the solar cell to increase the power density and maximize the intensity of UC luminescence. To realize this, dielectric-filled compound parabolic concentrators (CPCs) were used as integrated optics on the rear side of a planar bifacial silicon solar cell together with a 25% Er3+ doped hexagonal sodium yttrium fluoride (β-NaYF4:Er) UC phosphor. An efficiency increase of 32% from 0.123% to 0.163% under sub-band-gap illumination is quantified by means of the first ever reported I–V characteristics for an up-conversion solar cell (UC-SC) based on c-Si. An enhancement in external quantum efficiency (EQE) is obtained from 1.33% for the non-concentrating reference UC-SC to 1.80% for a solar cell with integrated optics for an excitation at 1523 nm with an irradiance of 0.024 W/cm2, corresponding to a normalized EQE of 0.75 W/cm2. This demonstrates that CPCs are suitable for UC-SC as they increase the concentration in the forwards direction, while maintaining high collection efficiency of the UC emission in the reverse direction. In addition, such an approach enables the optimization of the solar concentration on the UC phosphor independently from the concentration required for the solar cell.
    Solar Energy Materials and Solar Cells 07/2015; 140:217–223. DOI:10.1016/j.solmat.2015.04.020 · 5.34 Impact Factor
  • Source
    • "Due to the precipitation of fluoride nanocrystals, the local environment around rare-earth ions changes from oxides to fluorides with low effective phonon energy. This change decreases the non-radiative probabilities of certain energy levels of rare earth ions, and results in increased visible and infrared luminescence [6]. The changes in local environment of rare earth ions have been inferred from the changes in lifetimes of certain energy levels [7] [8]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Nd3 + and Tm3 +, doped oxy-fluoride glasses and glass ceramics were prepared by conventional melt-quenching and subsequent heat-treatment, respectively. β-PbF2 nanocrystals with diameter 50 -100 nm formed in the glass matrix after heat treatment. The Stark splitting in absorption peaks, enhanced photoluminescence and prolonged lifetimes that β-PbF2 nanocrystal formation increased the luminescence of rare earth ions. Both Nd3 + and Tm3 + ions were incorporated into nanocrystals that were enriched in lead and fluorine, and deficient in oxygen.
    Materials Characterization 10/2014; 98. DOI:10.1016/j.matchar.2014.10.020 · 1.85 Impact Factor
  • Source
    • "nm, indicating higher population of excited states [3]. The shift of the peaks between the reference and the CPC-45 ο UC-PV device however, is independent of the UC phosphor or the configuration and is an artefact caused during acquisition of the data. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we incorporate non-imaging optics in up-conversion-photovoltaic (UC-PV) devices based on -NaYF4:Er3+ and planar bifacial silicon solar cells with antireflective coatings optimised for UC. The UC-PV devices were characterised under monochromatic illumination covering the excitation spectrum of the UC phosphor between 1450 and 1590 nm. Here, we present recent results that exhibit up to a two-fold increase in external quantum efficiency of UC-PV devices. This is not only a significant enhancement compared to UC-PV devices without any concentrating optics, but introduces a novel concept that enables system integration and could lead to additional enhancement after further optimisation.
    29th European Photovoltaic Solar Energy Conference and Exhibition, Amsterdam, the Netherlands; 09/2014
Show more