Tuning upconversion through energy migration in core–shell nanoparticles

Wang, Feng; Deng, Renren; Wang, Juan; Wang, Qingxiao; Han, Yu; Zhu, Haomiao; Chen, Xueyuan; Liu, Xiaogang

doi:10.1038/nmat3149

Cited by 1,633 publications

(1,117 citation statements)

References 48 publications

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“…This means that the cross-relaxation rate of the 1 G 4 level in a nearest-neighbor pair is 1/0.16 ms, 6603 faster than radiative decay. Such fast cross-relaxation rates explain why in upconversion experiments only low Tm 31 concentrations of no higher than 1% yield bright blue upconversion emission [44][45][46] .…”

Section: Resultsmentioning

confidence: 98%

Multi-photon quantum cutting in Gd2O2S:Tm3+ to enhance the photo-response of solar cells

Martín-Rodríguez

Zhang

et al. 2015

Light Sci Appl

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Conventional photoluminescence (PL) yields at most one emitted photon for each absorption event. Downconversion (or quantum cutting) materials can yield more than one photon by virtue of energy transfer processes between luminescent centers. In this work, we introduce Gd 2 O 2 S:Tm 31 as a multi-photon quantum cutter. It can convert near-infrared, visible, or ultraviolet photons into two, three, or four infrared photons of ,1800 nm, respectively. The cross-relaxation steps between Tm 31 ions that lead to quantum cutting are identified from (time-resolved) PL as a function of the Tm 31 concentration in the crystal. A model is presented that reproduces the way in which the Tm 31 concentration affects both the relative intensities of the various emission lines and the excited state dynamics and providing insight in the quantum cutting efficiency. Finally, we discuss the potential application of Gd 2 O 2 S:Tm 31 for spectral conversion to improve the efficiency of next-generation photovoltaics. Keywords: downconversion; infrared emission; quantum cutting; solar cells; spectral conversions INTRODUCTION Over the last decade, advanced luminescent materials exhibiting downconversion, also known as quantum cutting or quantum splitting, have been developed 1,2 . In this process, a high-energy photon is converted into two or more lower-energy photons, with a quantum efficiency of potentially well over 100% 3 . If the downconverted photons are in the visible range, this concept is of interest for color conversion layers in conventional lighting applications 1,2,4-6 . New exciting possibilities of downconversion to infrared (IR) photons lie in next-generation photovoltaics, aiming at minimizing the spectral mismatch losses in solar cells [7][8][9][10][11] .Spectral mismatch is the result of the broad width of the spectrum emitted by the sun. Semiconductor absorber materials absorb only photons with an energy hn higher than the band gap E g 7 . To absorb many photons and produce a large electrical current, absorber materials must therefore have a small bandgap. However, because excited charge carriers rapidly thermalize to the edges of a semiconductor's conduction and valence bands, a high voltage output requires an absorber with a large band gap. Hence, materials with low transmission losses (leading to a large current) have high thermalization losses (leading to a low voltage) and vice versa 12,13 . These spectral mismatch losses constitute the major factor defining the relatively low ShockleyQueisser limit 14 , the maximum light-to-electricity conversion efficiency of 33% in a single-junction solar cell, obtained for a band gap of approximately 1.1 eV (1100 nm) 13 .Efficiencies higher than 33% can be reached with multi-junction solar cells, where a stack of multiple absorber materials are each optimized to efficiently convert different parts of the solar spectrum to

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Section: Resultsmentioning

confidence: 98%

Multi-photon quantum cutting in Gd2O2S:Tm3+ to enhance the photo-response of solar cells

Martín-Rodríguez

Zhang

et al. 2015

Light Sci Appl

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“…Through the Gd 3+ sublattice, the excitation energy can migrate with fast rates over a long distance in favor of energy transfer processes 152, 162. Energy migration‐mediated upconversion in core/shell nanoparticles synergistically combines the advantages of a core/shell structure and the fast energy migration effect, enhancing the anti‐Stokes emissions 163, 164.…”

Section: Effects Of Nir Light Power Intensity On the Upconverting Phementioning

confidence: 99%

Lanthanide‐Doped Upconversion Nanoparticles: Emerging Intelligent Light‐Activated Drug Delivery Systems

et al. 2016

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The development of drug delivery systems (DDSs) using near infrared (NIR) light and upconversion nanoparticles (UCNPs) has generated intensive interest over the past five years. These NIR‐initiated DDSs not only offer a high degree of spatial and temporal determination of therapeutic release but also provide precise control over the released dosage. Furthermore, these nanoplatforms confer several advantages over conventional light‐based DDSs—NIR offers better tissue penetration depth and a reduced risk of cellular photo‐damage caused by exposure to light at high‐energy wavelengths (e.g., ultraviolet light, <400 nm). The development of DDSs that can be activated by low intensity NIR illumination is highly desirable to avoid exposing living tissues to excessive heat that can limit the in vivo application of these DDSs. This encompasses research in three directions: (i) enhancing the quantum yield of the UCNPs; (ii) incorporation of photo‐responsive materials with red‐shifted absorptions into the UCNPs; and (iii) tuning the UCNPs excitation wavelength. This review focuses on recent advances in the development of NIR‐initiated DDS, with emphasis on the use of photo‐responsive compounds and polymeric materials conjugated onto UCNPs. The challenges that limit UCNPs clinical applications, alongside with the aforementioned techniques that have emerged to overcome these limitations, are highlighted.

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“…A superior optical property of NaYF 4 :Yb,Er@NaYF 4 :Yb,Tm was reported to that of NaYF 4 :Yb,Er,Tm 64. Furthermore, in 2011, Wang et al proposed a theory named energy migration upconversion (EMU), which is actually a long range ETU interaction 15. As Figure 3 a,b shows, the excitation energy is absorbed by Yb 3+ ions, and accumulated by Tm 3+ ions in the core area.…”

Section: Energy Transfermentioning

confidence: 99%

Current Advances in Lanthanide‐Doped Upconversion Nanostructures for Detection and Bioapplication

2016

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Along with the development of science and technology, lanthanide‐doped upconversion nanostructures as a new type of materials have taken their place in the field of nanomaterials. Upconversion luminescence is a nonlinear optical phenomenon, which absorbs two or more photons and emits one photon. Compared with traditional luminescence materials, upconversion nanostructures have many advantages, such as weak background interference, long lifetime, low excitation energy, and strong tissue penetration. These interesting nanostructures can be applied in anticounterfeit, solar cell, detection, bioimaging, therapy, and so on. This review is focused on the current advances in lanthanide‐doped upconversion nanostructures, covering not only basic luminescence mechanism, synthesis, and modification methods but also the design and fabrication of upconversion nanostructures, like core–shell nanoparticles or nanocomposites. At last, this review emphasizes the application of upconversion nanostructure in detection and bioimaging and therapy. Learning more about the advances of upconversion nanostructures can help us better exploit their excellent performance and use them in practice.

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Tuning upconversion through energy migration in core–shell nanoparticles

Cited by 1,633 publications

References 48 publications

Multi-photon quantum cutting in Gd2O2S:Tm3+ to enhance the photo-response of solar cells

Multi-photon quantum cutting in Gd2O2S:Tm3+ to enhance the photo-response of solar cells

Lanthanide‐Doped Upconversion Nanoparticles: Emerging Intelligent Light‐Activated Drug Delivery Systems

Current Advances in Lanthanide‐Doped Upconversion Nanostructures for Detection and Bioapplication

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