| 1. |
- Zhang, Liangdong, et al.
(författare)
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Bright Free Exciton Electroluminescence from Mn-Doped Two-Dimensional Layered Perovskites
- 2019
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 10:11, s. 3171-3175
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) perovskites incorporating hydrophobic organic spacer cations show improved film stability and morphology compared to their three-dimensional (3D) counterparts. However, 2D perovskites usually exhibit low photoluminescence quantum efficiency (PLQE) owing to strong exciton-phonon interaction at room temperature, which limits their efficiency in light-emitting diodes (LEDs). Here, we demonstrate that the device performance of 2D perovskite LEDs can be significantly enhanced by doping Mn(2+)in (benzimidazolium)(2)PbI4 2D perovskite films to suppress the exciton-phonon interaction. The distorted [PbI6](4-) octahedra by Mn-doping and the rigid benzimidazolium (BIZ) ring without branched chains in the 2D perovskite structure lead to improved crystallinity and rigidity of the perovskites, resulting in suppressed phonon-exciton interaction and enhanced PLQE. On the basis of this strategy, for the first time, we report yellow electroluminescence from free excitons in 2D (n = 1) perovskites with a maximum brightness of 225 cd m(-2) and a peak EQE of 0.045%.
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| 2. |
- Yang, Rong, et al.
(författare)
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Oriented Quasi-2D Perovskites for High Performance Optoelectronic Devices
- 2018
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 30:51
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Tidskriftsartikel (refereegranskat)abstract
- Quasi-2D layered organometal halide perovskites have recently emerged as promising candidates for solar cells, because of their intrinsic stability compared to 3D analogs. However, relatively low power conversion efficiency (PCE) limits the application of 2D layered perovskites in photovoltaics, due to large energy band gap, high exciton binding energy, and poor interlayer charge transport. Here, efficient and water-stable quasi-2D perovskite solar cells with a peak PCE of 18.20% by using 3-bromobenzylammonium iodide are demonstrated. The unencapsulated devices sustain over 82% of their initial efficiency after 2400 h under relative humidity of approximate to 40%, and show almost unchanged photovoltaic parameters after immersion into water for 60 s. The robust performance of perovskite solar cells results from the quasi-2D perovskite films with hydrophobic nature and a high degree of electronic order and high crystallinity, which consists of both ordered large-bandgap perovskites with the vertical growth in the bottom region and oriented small-bandgap components in the top region. Moreover, due to the suppressed nonradiative recombination, the unencapsulated photovoltaic devices can work well as light-emitting diodes (LEDs), exhibiting an external quantum efficiency of 3.85% and a long operational lifetime of approximate to 96 h at a high current density of 200 mA cm(-2) in air.
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| 3. |
- Chen, Mingming, et al.
(författare)
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Ceria-carbonate composite for low temperature solid oxide fuel cell : Sintering aid and composite effect
- 2014
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 39:23, s. 12309-12316
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of carbonate content on microstructure, relative density, ionic conductivity and fuel cell performance of Ce0.8Sm0.2O1.9-(Li/Na)(2)CO3 (SDC-carbonate, abbr. SCC) composites is systematically investigated. With the addition of carbonate, the nanoparticles of ceria are well preserved after heat-treatment. The relative densities of SCC pellets increase as the carbonate content increases or sintering temperature rises. Especially, the relative density of SCC2 sintered at 900 degrees C is higher than that of pure SDC sintered at 1350 degrees C. Both the AC conductivity and DC oxygen ionic conductivity are visibly improved compared with the single phase SDC electrolyte. Among the composites, SDC-20 wt% (Li/Na)(2)CO3 (SCC20) presents high dispersion, relative small particle size, and the dense microstructure. The optimized microstructure brings the best ionic conductivity and fuel cell performance. It is hoped that the results can contribute the understanding of the role of carbonate in the composite materials and highlight their prospective application.
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| 4. |
- Fan, Liangdong, et al.
(författare)
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Electrochemical study of lithiated transition metal oxide composite as symmetrical electrode for low temperature ceramic fuel cells
- 2013
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 38:26, s. 11398-11405
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Tidskriftsartikel (refereegranskat)abstract
- In this work, Lithiated NiCuZnOx (LNCZO) composite is synthesized and evaluated as a potential symmetrical electrode for ceria-carbonate composite electrolyte based low temperature ceramic fuel cells. Its crystal structures, the hydrogen oxidation/oxygen reduction electrochemical activities and fuel cell performances are systematically examined on the symmetrical cell configuration. Nano crystallite particles in the form of composite are observed for these oxides. The LNCZO shows relatively high catalytic activities for hydrogen oxidation and oxygen reduction reaction according to the electrochemical impedance spectroscopy measurements. A remarkable low oxygen reduction activation energy of 42 kJ mol(-1) is obtained on the LNCZO/ceria-carbonate composite, demonstrating excellent electro-catalytic activity. Especially, the catalytic activity can be further improved in the presence of water in the cathode chamber. The results show that the lithiated transition metal oxide composite is a promising symmetrical electrode for ceria-carbonate electrolyte and composite approach might a probable solution to develop super-performance electrodes for reduced temperature ceramic fuel cells.
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| 5. |
- Fan, Liangdong, et al.
(författare)
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Proton and Oxygen Ionic Conductivity of Doped Ceria-Carbonate Composite by Modified Wagner Polarization
- 2012
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Ingår i: International Journal of Electrochemical Science. - 1452-3981. ; 7:9, s. 8420-8435
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Tidskriftsartikel (refereegranskat)abstract
- The impressive ionic conductivity and tunable conduction behaviors have made the ceria-carbonate composite an attractive electrolyte for low temperature ceramic fuel cells. However, the conduction mechanism is not yet well studied. In the present study, both proton and oxygen ion conductivity as well as the transport properties of samaria-doped ceria/ sodium-lithium-carbonate (denoted as SDCLN) composite are investigated by the fuel cell study and the modified Hebb-Wagner polarization measurements. The multi-ionic polarization behaviors and the transfer processes in composite electrolyte under external electrical field are analyzed. A maximum power density of 780 mW cm(-2) and a calculated total ion (proton and oxygen ion) conductivity of 0.153 S cm(-1) are obtained under H-2/air condition at 550 degrees C. The Wagner DC polarization measurements show that the proton conduction dominates the total ionic conductivity. A synergistic effect exists between the charge carriers in the doped ceria-carbonate composite system. An ideal interfacial conduction model is also proposed based on the obtained results.
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| 6. |
- He, Yunjuan, et al.
(författare)
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Cobalt oxides coated commercial Ba0.5Sr0.5Co0.8Fe0.2O3-delta as high performance cathode for low-temperature SOFCs
- 2016
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 191, s. 223-229
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Tidskriftsartikel (refereegranskat)abstract
- In order to improve the catalytic activity of commercial Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) for low-temperature solid oxide fuel cells (LTSOFC) (300-600 degrees C), CoOx has been used to modify the commercial BSCF through a solution coating approach. Phase and morphology of samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive spectrometry (EDS), respectively. BSCF with 10 wt% CoOx exhibited an improved conductivity of 44 S/cm, and achieved a peak power density of 463 mW/cm(2) at 550 degrees C for LTSOFC, which is a 100% enhancement than that with the BSCF cathode. The cathode oxygen reduction reaction (ORR) promoted by CoOx and enhanced device performance mechanism have been proposed. This work provides a new way for the exploitation of high effective cathode materials for LTSOFCs.
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| 7. |
- Liu, Yanyan, et al.
(författare)
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Superionic Conductivity of Sm3+, Pr3+, and Nd3+ Triple-Doped Ceria through Bulk and Surface Two-Step Doping Approach
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:28, s. 23614-23623
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Tidskriftsartikel (refereegranskat)abstract
- Sufficiently high oxygen ion conductivity of electrolyte is critical for good performance of low-temperature solid oxide fuel cells (LT-SOFCs). Notably, material conductivity, reliability, and manufacturing cost are the major barriers hindering LT-SOFC commercialization. Generally, surface properties control the physical and chemical functionalities of materials. Hereby, we report a Sm3+, Pr3+, and Nd3+ triple-doped ceria, exhibiting the highest ionic conductivity among reported doped-ceria oxides, 0.125 S cm(-1) at 600 degrees C. It was designed using a two-step wet-chemical coprecipitation method to realize a desired doping for Sm3+ at the bulk and Pr3+/Nd3+ at surface domains (abbreviated as PNSDC). The redox couple Pr3+ Pr4+ contributes to the extraordinary ionic conductivity. Moreover, the mechanism for ionic conductivity enhancement is demonstrated. The above findings reveal that a joint bulk and surface doping methodology for ceria is a feasible approach to develop new oxide-ion conductors with high impacts on advanced LT-SOFCs.
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| 8. |
- Mi, Youquan, et al.
(författare)
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Rare-earth oxide Li0.3Ni0.9Cu0.07Sr0.03O2-delta composites for advanced fuel cells
- 2017
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Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 42:34, s. 22214-22221
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Tidskriftsartikel (refereegranskat)abstract
- Recent development on electrolyte-free fuel cell (EFFC) holding the same function with the traditional solid oxide fuel cell (SOFC) but with a much simpler structure has drawn increasing attention. Herein, we report a composite of industrial grade rare-earth precursor for agriculture and Li0.3Ni0.9Cu0.07Sr0.03O2.a, (RE-LNCS) for EFFCs. Both structural and electrical properties are investigated on the composite. It reveals that the RE LNCS possesses a comparable ionic and an electronic conductivities, 0.11 S cm(-1) and 0.20 S cm(-1) at 550 degrees C, respectively. An excellent power output of 1180 mW cm(-2) has been achieved at 550 degrees C, which is much better than that of the conventional anode/electrolyte/cathode based SOFCs, only around 360 mW cm(-2) by using ionic conducting rare-earth material as the electrolyte. Engineering large size cells with active area of 25 cm(2) prepared by tape-casting and hot-pressing gave a power output up to 12 W. This work develops a new functional single layer composite material for EFFCs and further explores the device functions.
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| 9. |
- Miao, Yanfeng, et al.
(författare)
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Stable and bright formamidinium-based perovskite light-emitting diodes with high energy conversion efficiency
- 2019
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Solution-processable perovskites show highly emissive and good charge transport, making them attractive for low-cost light-emitting diodes (LEDs) with high energy conversion efficiencies. Despite recent advances in device efficiency, the stability of perovskite LEDs is still a major obstacle. Here, we demonstrate stable and bright perovskite LEDs with high energy conversion efficiencies by optimizing formamidinium lead iodide films. Our LEDs show an energy conversion efficiency of 10.7%, and an external quantum efficiency of 14.2% without outcoupling enhancement through controlling the concentration of the precursor solutions. The device shows low efficiency droop, i.e. 8.3% energy conversion efficiency and 14.0% external quantum efficiency at a current density of 300 mA cm(-2), making the device more efficient than state-of-the-art organic and quantum-dot LEDs at high current densities. Furthermore, the half-lifetime of device with benzylamine treatment is 23.7 hr under a current density of 100 mA cm(-2), comparable to the lifetime of near-infrared organic LEDs.
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| 10. |
- Schoch, Conrad L., et al.
(författare)
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Finding needles in haystacks: linking scientific names, reference specimens and molecular data for Fungi
- 2014
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Ingår i: Database: The Journal of Biological Databases and Curation. - : Oxford University Press (OUP). - 1758-0463. ; 2014:bau061, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- DNA phylogenetic comparisons have shown that morphology-based species recognition often underestimates fungal diversity. Therefore, the need for accurate DNA sequence data, tied to both correct taxonomic names and clearly annotated specimen data, has never been greater. Furthermore, the growing number of molecular ecology and microbiome projects using high-throughput sequencing require fast and effective methods for en masse species assignments. In this article, we focus on selecting and re-annotating a set of marker reference sequences that represent each currently accepted order of Fungi. The particular focus is on sequences from the internal transcribed spacer region in the nuclear ribosomal cistron, derived from type specimens and/or ex-type cultures. Re-annotated and verified sequences were deposited in a curated public database at the National Center for Biotechnology Information (NCBI), namely the RefSeq Targeted Loci (RTL) database, and will be visible during routine sequence similarity searches with NR_prefixed accession numbers. A set of standards and protocols is proposed to improve the data quality of new sequences, and we suggest how type and other reference sequences can be used to improve identification of Fungi.
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