Experimental enhancement of the photocurrent in a solar cell using upconversion process in fluoroindate glasses exciting at 1480 nm (original) (raw)
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Infrared, blue and ultraviolet upconversion emissions in Yb3+–Tm3+-doped fluoroindate glasses
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1999
Intense ultraviolet (362.5 nm), blue (479 nm) and IR (800 nm) upconversion emissions were obtained in fluoroindate glasses co-doped with Yb 3 + and Tm 3 + ions pumped at 975 nm. The dependence of these upconversion emissions on excitation intensity has been studied and it is concluded that emissions come from Tm 3 + ions excited by successive energy transfers from Yb 3 + ions. The temporal evolution of the 800 nm upconversion emission obtained under flash excitation at 975 nm cannot be described using the energy migration model. This indicates that at this concentration of Yb 3 + , the rapid migration regime among these ions has not been reached. A model is proposed in order to explain the temporal evolution of this emission, taking into account back-transfer processes from Tm 3 + to Yb 3 + ions.
EPJ Photovoltaics, 2011
Upconverted emission from erbium ions in fluoride materials (glass and disordered crystal of the system CaF2-YF3) are observed in a wide spectral range (from the visible to the near infrared) under infrared excitation at 1.54 μm. In both cases, the upconverted emission in the near infrared (∼1 μm) dominates the spectrum. Absolute UC efficiency defined as the ratio between the UC luminescence power and the absorbed pump power has been experimentally measured. The NIR (∼1 μm) luminescence energy yield for the glass and the disordered crystal varies from 2.4 to 11.5% for the glass and from 7.7 to 16% for the crystal for an infrared excitation power density ranging from 2 W/cm 2 to 100 W/cm 2. This is of a particular interest for their use as upconverter to improve the c-Si cells quantum efficiency since the energy of the excitation lies below the c-Si absorption edge (1.12 eV at 300 K) and is well located compared to the AM1.5G solar spectrum, outside of the absorption lines due to different atmospheric gases. Furthermore, the most efficient upconverted emission recorded in the investigated materials occurs at an energy just above the gap. A current generated in a bifacial c-Si solar cell is observed when the Er 3+ doped material (1.55 mA and 2.15 mA for the glass and the crystal respectively), placed at the rear face of the cell, is excited at 1.54 μm. The current dependence as a function of the sub-bandgap excitation power has been measured and modelled. Finally the EQE of the complete device is deduced from the measured shortcircuit current and the incident photon flux on the cell. An increase of the cell quantum efficiency of 2.4% and 1.7% is obtained at 1.54 μm with adding the glass and the crystal respectively at the rear face of the c-Si cell. The results are compared to those already obtained with Er: NaYF4 known as the most efficient upconverter. This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial License 3.0, which permits unrestricted use, distribution, and reproduction in any noncommercial medium, provided the original work is properly cited. 20601-p2 F. Pellé et al.: Upconversion of 1.54 μm radiation in Er 3+ doped materials for c-Si solar cell
Upconversion of infrared-to-visible light in Pr 3+–Yb 3+ codoped fluoroindate glass
Optics Communications, 1998
Bright fluorescence in the visible range has been observed in Pr 3q -Yb 3q doped fluoroindate glass under infrared diode laser irradiation. The mechanism which contributes for the upconversion emission is identified and the energy transfer rate between Pr 3q -Yb 3q is obtained for different concentrations. q
Optical Materials, 2010
Up-conversion luminescence of oxyfluoride glass and glass ceramics containing LaF 3 crystallites doped with Yb 3+ and Er 3+ was investigated at low temperature. Excitation of Yb 3+ in the IR region revealed the fast and the slow components of Er 3+ up-conversion luminescence originating from both glass and crystalline phases. The temporal differences of the both kinds of the luminescence allowed reconstructing the excitation spectra of the up-conversion luminescence related to the glass and crystalline phases in the glass ceramics.
Upconversion luminescence dynamics of Er-doped fluoride crystals for optical converters
Journal of Luminescence, 2008
ABSTRACT Erbium (Er)-doped fluoride crystals (YLF, BYF, CaF2, etc.) are well-known as active media for solid-state lasers emitting in IR and VIS spectral domains, and as materials for efficient near-IR to VIS upconversion. In this paper, we report on the study of conversion of IR light from an ∼1.5 μm spectral region to an ∼1 μm spectral domain in low-phonon RE-doped fluoride crystals CaF2 (RE=Er3+ Yb3+). Energy transfer processes taking place at selective pulsed and CW laser excitation are investigated experimentally. It is shown that in the CaF2:RE crystals efficient conversion of IR radiation from the ∼1.5 μm region to the ∼1 μm region occurs, and these crystals are perspective for using in spectral converters for enhancing solar cell efficiency.
Strong 153 μm to NIR-VIS-UV upconversion in Er-doped fluoride glass for high-efficiency solar cells
Journal of the Optical Society of America B, 2009
Optical spectra of Er-doped modified ZBLAN glasses are studied at room temperature. Radiative quantum yields of the 4 I 11/2 and 4 I 13/2 levels are estimated from the experimentally measured lifetimes and from the spontaneous emission probabilities calculated from the Judd-Ofelt theory. The spectra of upconversion (UC) luminescence excited with 1.53 m cw Er fiber laser are investigated in a wide spectral domain [from the nearinfrared (NIR) to UV]. Absolute UC efficiency (i.e., the ratio of UC luminescence power to the absorbed pump power) is experimentally measured; efficiency of up to 12.7% is obtained. A conclusion is made about perspectives of use of the studied glasses as upconverter material for solar cells of enhanced efficiency.
Upconversion mechanisms in rare-earth doped glasses to improve the efficiency of silicon solar cells
Solar Energy Materials and Solar Cells, 2011
The electronic energy transfer properties between Ho 3 + and Yb 3 + ions have been studied in a fluoroindate glass for solar cell applications. The Ho 3 + ions absorb infrared radiation at around 1150 nm, below the energy gap of Si solar cells. Energy transfer between Ho 3 + and Yb 3 + ions produces an upconversion emission in the visible and in the near infrared spectral range just above the Si bandgap. When these glasses are placed at the rear of a bifacial Si solar cell, the upconverted radiation can be absorbed by Si and generate electron-hole pairs that contribute to enhance the cell efficiency. An estimation of the expected increase in photo-current has been calculated when the upconverter material is used in a solar concentrator. Besides, they can be used alone or together with other Er 3 + doped phosphors for the same purpose. The Ho 3 + -Yb 3 + upconversion emission characteristics have been investigated as a function of the doping ion concentrations. Excitation, pump power dependency and dynamic experiments have been performed to determine the electronic energy transfer mechanism that is responsible of the upconversion. A rate equation analysis shows a reasonable agreement between the model and the experimental data.
Journal of Non-Crystalline Solids, 2008
Energy-transfer excited upconversion luminescence in Ho 3+ /Yb 3+ -and Tb 3+ /Yb 3+ -codoped PbGeO 3 -PbF 2 -CdF 2 glass and glassceramic under infrared excitation is investigated. In Ho 3+ /Yb 3+ -codoped samples, green (545 nm), red (652 nm), and near-infrared (754 nm) upconversion emission corresponding to the 5 S 2 ( 5 F 4 ) ! 5 I 8 , 5 F 5 ! 5 I 8 , and 5 S 2 ( 5 F 4 ) ! 5 I 7 transitions, respectively, was observed. Blue (490 nm) emission assigned to the 5 F 2,3 ! 5 I 8 transition was also detected. In the Tb 3+ /Yb 3+ -codoped system, bright UV-visible emission around 384, 415, 438, 473-490, 545, 587, and 623 nm, identified as due to the 5 D 3 ( 5 G 6 ) ! 7 F J (J = 6, 5, 4) and 5 D 4 ! 7 F J (J = 6, 5, 4, 3) transitions, was measured. The comparison of the upconversion process in glass ceramic and its glassy precursor revealed that the former samples present much higher upconversion efficiencies. The dependence of the upconversion emission upon pump power, and doping contents was also examined. The results indicated that successive energy-transfer between ytterbium and holmium ions and cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The viability of using the samples for three-dimensional solid-state color displays is also discussed.
Journal of Applied Physics, 2000
Infrared-to-visible upconversion emission enhancement through thermal effects in Yb 3ϩ-sensitized Pr 3ϩ-doped fluoroindate glasses excited at 1.064 m is investigated. A twentyfold increase in the 485 nm blue emission intensity as the sample temperature was varied from 20 to 260°C was observed. The visible upconversion fluorescence enhancement is ascribed to the temperature dependent multiphonon-assisted anti-Stokes excitation of the ytterbium sensitizer and excited-state absorption of the praseodymium acceptor. A model based upon conventional rate equations considering a temperature dependent effective absorption cross section for the 2 F 7/2 → 2 F 5/2 transition of the Yb 3ϩ and 1 G 4 → 3 P 0 excited-state absorption of the Pr 3ϩ , agrees very well with the experimental results.
An intensity enhancement of the green upconversion emission from a codoped Er 3+ -Yb 3+ fluoroindate glass has been obtained by coating the glass surface with silica microspheres (3.8 µm diameter). The microspheres focus an incoming beam (λ ≈950 nm) on the surface of the fluoroindate glass. The green emission (λ ≈545 nm) of the Er 3+ ions located in the microsphere focus was measured with a microscope in reflection mode, being the peak intensity 4.5 times the emission of the bare substrate. The transversal FWHM of the upconversion spot was experimentally determined by deconvolution with the experimental Point Spread Function of the system, obtaining a value of 309 nm. This value is in good agreement with Finite-Difference Time-Domain simulations taking into account the magnification of the image due to the microsphere.