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1.
J Colloid Interface Sci ; 559: 162-168, 2019 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-31627139

RESUMO

Multifunctional materials have attracted recent attention due to their various applications in many fields. In this work, CaWO4 nanocrystals were prepared by a hydrothermal method. Nanoparticles, nanowires, and micro-sized structures were obtained by controlling the reaction temperature, Ca2+-to-WO42- ratio and type of dopant. The influence of rare earth ions on the morphology and luminescence properties was investigated. Upconversion and downconversion luminescence behaviors showed CaWO4 to be an excellent host for rare earth doping. CaWO4:Er3+ nanowires were also used in dye-sensitized solar cells (DSSCs) to improve device performance. Increased light harvesting caused by improved dye loading capacity and enhanced light scattering led to improved cell efficiency. Moreover, reduced charge recombination due to the additional energy levels of CaWO4:Er3+ was another reason for the improved cell efficiency. Therefore, in this work, we demonstrated the synthesis of CaWO4 nanocrystals and the control of their morphology and luminescence by rare earth doping, which has significant future applications in lighting and display. The applications in DSSCs provide a new strategy to achieve high-performance solar cells by using nanocrystals via increased light harvesting and reduced charge recombination.

2.
ACS Appl Mater Interfaces ; 11(37): 33868-33878, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31441638

RESUMO

Growing attention has been paid to CsPbIBr2 perovskite solar cells (PSCs) after balancing the band gap and stability features of the interested full-inorganic perovskites. However, their power-conversion efficiency (PCE) still lags behind that of the PSCs using hybrid halide perovskite and how to increase the corresponding PCE is still a challenge. Herein, antisolvents and organic ion surface passivation strategies were systematically applied to precisely control the growth of CsPbIBr2 crystals for constructing a high-quality full-inorganic perovskite film. Through careful adjustments, a CsPbIBr2 film with a pure phase, full coverage, and high crystallinity with preferable (100) orientation was successfully obtained by introducing diethyl ether as the antisolvent followed by guanidinium surface passivation. The optimal CsPbIBr2 film was composed by a large grain with an average size of 950 nm, few grain boundaries, and higher hydrophobic property. Planer PSC using the optimal CsPbIBr2 film and electron-beam-deposited TiO2 compact layer exhibits a PCE of 9.17%, which ranks among the highest PCE range of the reported CsPbIBr2 PSCs. Besides, the designed CsPbIBr2 PSC exhibited good long-term stability, which could maintain 90% of the initial PCE in 40% humidity ambient, which remained constant after heat treatment at 100 °C for 100 h. Based on the optimal CsPbIBr2 film, the flexible and large-area (up to 225 mm2) PSCs were further fabricated. The adopted film improvement methods were further extended to other kinds of full-organic PSCs, which demonstrated the universality of this strategy.

3.
J Colloid Interface Sci ; 553: 14-21, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31176975

RESUMO

Perovskite solar cells (PSCs) had received great attention as a result of their recent rapid increasing efficiency. However, the stability of PSCs is still a challenge due to the degradation of the perovskite layer caused by the high-energy ultraviolet (UV) irradiation. Inspired by the luminescent down converting ability for UV blocking and conversion as well as energy transfer between suitable rare earth (RE) ions, a planar CH3NH3PbI3 perovskite solar cell using Sm3+ and Eu3+ co-doped TiO2 electron transfer layer was designed. By optimizing the Sm3+ and Eu3+ doping concentration, the REs co-doped TiO2 ETL combines the advantages of high electron extraction and lower interfacial recombination caused by REs introduction, a power conversion efficiency of 19.01% was obtained. In addition, benefit from the enhanced ability to convert UV light into visible light of the co-doped ETL, the PSCs can sustain higher than at least 80% of the original efficiency over 25 days of full sunlight irradiation or after 100 h of UV illumination. Moreover, since the low-temperature pulsed laser deposition was adopted in ETL fabrication process, the large area (225 mm2) and flexibility devices were further explored, with PCEs of 12.60% and 15.48%, respectively. This work indicates that Sm3+ and Eu3+ co-doped ETLs are effective and promising method to enhance the photovoltaic performance and UV stability of PSCs, which can be further applied in other PSCs with different ETLs and co-doping types.

4.
Biochem Biophys Res Commun ; 513(2): 460-464, 2019 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-30967269

RESUMO

Abscisic acid (ABA), one of phytohormones, is induced in response to abiotic stress to mediate plant acclimation to environmental challenge. Key players of the ABA-signaling pathway are the ABA-binding receptors (RCAR/PYR1/PYL), which perceive ABA and then inhibit PP2Cs to activate SnRK2s. Here, we report that a putative receptor-like cytoplasmic kinase (RLCK) in Arabidopsis named CARK6, which is a member of cytosolic ABA receptor kinases. We confirm that CARK6 interacts with ABA receptors, RCAR11-14 in vitro and in vivo. Induced overexpression of CARK6 in Arabidopsis enhances sensitivity to ABA by inhibition of seed germination and root elongation, and promotes the drought resistance. However, loss-of-function seedlings of cark6 are less sensitive to ABA and show reduced drought stress response with respect to water loss and stomatal aperture. In transgenic Arabidopsis complementation lines in the cark6 mutant background, stress responsivity was restored by CARK6. In conclusion, our data provide evidence that CARK6 plays a positive role in ABA signaling in Arabidopsis.

5.
ACS Appl Mater Interfaces ; 11(12): 11481-11487, 2019 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-30839191

RESUMO

Organic-inorganic lead halide perovskite solar cells (PSCs) exhibit spectacular changes in the photovoltaic area, but they still face the challenges of full spectral utilization and photostability under continuous light irradiation. The ultraviolet (UV) part in sunlight could induce oxygen vacancy in the mesoporous TiO2 (m-TiO2) layer, resulting in the degradation of perovskite photoactive films and the rapidly decreased device performance. In this work, we demonstrate that an effective luminescent downconversion material, Eu(TTA)2(Phen)MAA (ETPM), can be used as an interfacial modifier between the m-TiO2 layer and the perovskite photoactive layer to improve the power conversion efficiency (PCE) from 17.00 to 19.07%. The improved device performance can be ascribed to the effective utilization of incident UV light and reduced carrier recombination. Meanwhile, the conversion of the UV light by ETPM could inhibit the stability loss of the device under irradiation. As a result, the modified PSCs can maintain 86% of their initial value under continuous light soaking for 100 h, higher than that of 40% for the control device. This work indicates that the introduction of the luminescent downconversion material ETPM can successfully improve the PCE and photostability of PSCs.

6.
J Colloid Interface Sci ; 517: 194-203, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29425956

RESUMO

A simple and large-scale synthetic method of Mn doped ZnO (ZnO:Mn) was developed in this work. ZnO:Mn nanocrystals with hexagonal structure were prepared by thermal decomposition of zinc acetate and manganese acetate in the presence of oleylamine and oleic acid with different temperatures, ligand ratios, and Mn doping concentrations. The particle size (47-375 nm) and morphology (hexagonal nanopyramid, hexagonal nanodisk and irregular nanospheres) of ZnO:Mn nanocrystals can be controlled by the ratio of capping ligand, reaction temperature, reaction time and Mn doping concentration. The corresponding optical and magnetic properties were systemically studied and compared. All samples were found to be paramagnetic with antiferromagnetic (AFM) exchange interactions between the Mn moments in the ZnO lattice, which can be affected by the reaction conditions. The quantum dot sensitized solar cells (QDSSCs) were fabricated based on ZnO:Mn nanocrystals and CdS quantum dots, and the device performance affected by Mn doping concentration was also studied and compared.

7.
ACS Appl Mater Interfaces ; 9(49): 42875-42882, 2017 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-29168634

RESUMO

Perovskite solar cells (PSCs) have attracted extensive attention due to their impressive photovoltaic performance. The quality of the perovskite layer is very critical to achieve high device performance. Here, we explore the partial substitution of PbI2 by ZnCl2 in the preparation of CH3NH3PbI3 and its effects on perovskite morphology, optical properties, and photovoltaic performance. Consequently, the device with 3% ZnCl2 shows great improvement in power conversion efficiency (PCE) from 16.4 to 18.2% compared to that of the control device. Moreover, the device is more stable than the control device, with only 7% degradation after aging for 30 days. These results are attributed to the increased grain size, improved film morphology, and reduced recombination loss after the partial substitution of PbI2 by ZnCl2 in the perovskite film. This work develops a new approach for morphology control through rational additives in the perovskite film, and paves the way toward further enhancing the device performances of PSCs including PCE and stability.

8.
ACS Appl Mater Interfaces ; 9(16): 14518-14524, 2017 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-28387496

RESUMO

Perovskite solar cells (PSCs) with high efficiency have recently received tremendous attention, but the stability under light irradiation, namely, photostability, of PSCs still represents a major obstacle that must be overcome before their practical applications can be used. The degeneration of perovskite under ultraviolet irradiation from sunlight is a major impacting factor. To solve this problem, in this work we introduce fluorescent carbon dots (CDs), which could effectively convert ultraviolet to blue light in the mesoporous TiO2 (m-TiO2) layer of the traditional PSCs. As a result, CD-based devices exhibit an improved power conversion efficiency (PCE) of 16.4% on average compared to 14.6% for bare devices, and the light stability of CD-based devices is highly enhanced. These devices can maintain nearly 70% of the initial efficiency after 12 h of full sunlight illumination, while the bare devices maintain only 20% of the initial efficiency. This work indicates that fluorescent down conversion based on CDs is a novel and effective approach to improve the performance and photostability of PSCs.

9.
Sci Rep ; 7: 39946, 2017 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-28059121

RESUMO

Lanthanide (Ln3+) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.

10.
Chem Commun (Camb) ; 52(68): 10354-6, 2016 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-27476744

RESUMO

Exchange coupling between magnetically hard and soft phases has the potential to yield a large gain in the energy product. In this work, we present a scalable chemical synthetic route to produce magnetic iron oxide based nanocomposites, consisting of cobalt ferrite (CoFe2O4) and strontium ferrite (SrFe12O19) components.

11.
J Colloid Interface Sci ; 480: 49-56, 2016 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-27399618

RESUMO

Co-sensitization by using two or more sensitizers with complementary absorption spectra to expand the spectral response range is an effective approach to enhance device performance of quantum dot sensitized solar cells (QDSSCs). To improve the light-harvesting in the visible/near-infrared (NIR) region, organic dye zinc phthalocyanine (ZnPc) was combined with CdS/CdSe quantum dots (QDs) for co-sensitized solar cells based on ZnO inverse opals (IOs) as photoanode. The resulting co-sensitized device shows an efficient panchromatic spectral response feature to ∼750nm and presents an overall conversion efficiency of 4.01%, which is superior to that of the individual ZnPc-sensitized solar cells and CdS/CdSe-sensitized solar cells. Meanwhile, an Au nanoparticles/graphene oxide (Au NPs/GO) composite layer was successfully prepared to modify Cu2S counter electrode for the co-sensitized solar cells. Reducing the carrier recombination process by GO and catalytic process of Au NPs leads to increased power conversion efficiency(PCE) from 4.01 to 4.60% and sustainable stability remains ∼85% of its original value after 60min light exposure. In this paper, introduction of the organic dyes as co-sensitizer and Au NPs/GO as counter electrode modified layer has been proved to be an effective route to improve the performance of QDSSCs.

12.
Angew Chem Int Ed Engl ; 55(35): 10439-43, 2016 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-27440206

RESUMO

Energy-storage concentration cells are based on the concentration gradient of redox-active reactants; the increased entropy is transformed into electric energy as the concentration gradient reaches equilibrium between two half cells. A recyclable and flow-controlled magnetic electrolyte concentration cell is now presented. The hybrid inorganic-organic nanocrystal-based electrolyte, consisting of molecular redox-active ligands adsorbed on the surface of magnetic nanocrystals, leads to a magnetic-field-driven concentration gradient of redox molecules. The energy storage performance of concentration cells is dictated by magnetic characteristics of cobalt ferrite nanocrystal carriers. The enhanced conductivity and kinetics of redox-active electrolytes could further induce a sharp concentration gradient to improve the energy density and voltage switching of magnetic electrolyte concentration cells.

13.
Nanotechnology ; 27(22): 225401, 2016 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-27103144

RESUMO

ZnS is typically used to passivate semiconductor quantum dots (QDs) prepared by the successive ionic layer adsorption and reaction (SILAR) method for solar cell applications, while for colloidal QDs, organic ligands are usually used for this passivation purpose. In this study we utilized oleylamine and oleic acid ligands, besides ZnS, to passivate QDs prepared by the SILAR approach, and investigated their effects on the incident photon-to-current efficiency (IPCE) performance of the solar cells. It was observed that oleylamine passivation decreased device performance, while oleic acid passivation improved the IPCE of the cells. Redshift of the IPCE onset wavelength was also observed after oleic acid coating, which was attributed to the delocalization of excitons in the CdS QDs.

14.
Nanotechnology ; 27(10): 10LT01, 2016 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-26866701

RESUMO

The phase transformation controlled tetragonality of MnNi nanostructures has attracted wide interest for their shape memory effect. In this study, MnNi nanocrystals were selected to epitaxially grow an FeCo shell, where the antiferromagnetic L1(0) phase transformation of the MnNi core triggers the tetragonal distortion in the magnetically soft FeCo shell. The tetragonality change of L1(0) MnNi under thermal annealing enables the control of the tetragonality of the FeCo phase, ultimately increasing magnetocrystalline anisotropy and coercivity. This study opens up a new route to fabricate functional nanostructures with unique magnetic properties.

15.
Nanotechnology ; 27(7): 07LT02, 2016 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-26783195

RESUMO

The dipolar interaction of magnetic nanoparticles is of intense interest to engineer material self-assembly for anisotropic functional nanostructures. Here we report the solution synthesis of cobalt nanowires, where the one-dimensional nanowire formation is ultimately dependent on the magnetic dipolar interaction to realize in situ assembly of cobalt nanoparticles. The morphology transition of cobalt nanostructures is well controlled via the ligand-free synthesis and thermal decomposition of zero-valent cobalt precursor. This study provides a self-assembly approach to the development of anisotropic cobalt nanostructures and a better understanding of nucleation parameters, which are demonstrated to correlate strongly with the size and morphology of final cobalt nanowires. This approach may be extended to other magnetic materials for the control of their nanostructure and magnetic performance.

16.
ACS Appl Mater Interfaces ; 8(14): 9071-9, 2016 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-26791114

RESUMO

Luminescent upconversion is a promising way to harvest near-infrared (NIR) sunlight and transforms it into visible light that can be directly absorbed by active materials of solar cells and improve their power conversion efficiency (PCE). However, it is still a great challenge to effectively improve the PCE of solar cells with the assistance of upconversion. In this work, we demonstrate the application of the transparent LiYF4:Yb(3+), Er(3+) single crystal as an independent luminescent upconverter to improve the PCE of perovskite solar cells. The LiYF4:Yb(3+), Er(3+) single crystal is prepared by an improved Bridgman method, and its internal quantum efficiency approached to 5.72% under 6.2 W cm(-2) 980 nm excitation. The power-dependent upconversion luminescence indicated that under the excitation of simulated sunlight the (4)F(9/2)-(4)I(15/2) red emission originally results from the cooperation of a 1540 nm photon and a 980 nm photon. Furthermore, when the single crystal is placed in front of the perovskite solar cells, the PCE is enhanced by 7.9% under the irradiation of simulated sunlight by 7-8 solar constants. This work implies the upconverter not only can serve as proof of principle for improving PCE of solar cells but also is helpful to practical application.

17.
ACS Appl Mater Interfaces ; 8(1): 31-6, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26709528

RESUMO

Ultrathin metal nanowires have attracted wide attention becau se oftheir unique anisotropy and surface-to-volume effects. In this study, we use ultrathin Au nanowires as the templating core to epitaxially grow magnetic iron-cobalt (FeCo) shell through metal-redox with the control on their thickness and stoichiometry. Large surface-stress-induced phase transformation in Au nanowires triggers and stabilizes metastable tetragonal FeCo nanostructure to enhance its magnetic anisotropy and coercivity. Meanwhile, under illumination, plasmon-induced hotspot in ultrathin Au nanowires enables the light-control on magnetic characteristics of FeCo shell. This study demonstrates the feasibility of surface-stress-induced phase transformation to stabilize and control metastable nanostructures for enhanced magnetic anisotropy, which is one of the key properties of functional magnetic materials.

18.
Sci Rep ; 5: 17684, 2015 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-26631493

RESUMO

In this work, we report a physical deposition based, compact (cp) layer synthesis for planar heterojunction perovskite solar cells. Typical solution-based synthesis of cp layer for perovskite solar cells involves low-quality of thin films, high-temperature annealing, non-flexible devices, limitation of large-scale production and that the effects of the cp layer on carrier transport have not been fully understood. In this research, using radio frequency magnetron sputtering (RFMS), TiO2 cp layers were fabricated and the thickness could be controlled by deposition time; CH3NH3PbI3 films were prepared by evaporation &immersion (E &I) method, in which PbI2 films made by thermal evaporation technique were immersed in CH3NH3I solution. The devices exhibit power conversion efficiency (PCE) of 12.1% and the photovoltaic performance can maintain 77% of its initial PCE after 1440 h. The method developed in this study has the capability of fabricating large active area devices (40 × 40 mm(2)) showing a promising PCE of 4.8%. Low temperature and flexible devices were realized and a PCE of 8.9% was obtained on the PET/ITO substrates. These approaches could be used in thin film based solar cells which require high-quality films leading to reduced fabrication cost and improved device performance.

19.
J Colloid Interface Sci ; 450: 196-201, 2015 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-25823724

RESUMO

One promising way to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs), which have attracted great interest due to their low cost, is modifying the working electrode. In this work, Tm and Yb doped as well as undoped In2O3 inverse opals (IOs) were synthesized by the sol-gel method. DSSCs based on In2O3, In2O3:Tm and In2O3:Yb IOs as photoanodes were fabricated and studied. It is observed that the device performance including open-circuit voltage (V(oc)) and short-circuit current (J(sc)) increased largely with the increasing pore size of the IOs and the introduction of Tm and Yb elements in the In2O3 lattices. The PCE of the DSSC was increased from 0.33% to 0.96% when the ln2O3 IOs photoanode was substituted by ln2O3:Yb IOs. The electrochemical impedance spectroscopy (EIS) measurements indicate that the modification of band gap in the Tm and Yb doped In2O3 IOs is significant for the improved performance, which can effectively suppress the charge transfer recombination and improve the electron lifetime.

20.
J Colloid Interface Sci ; 440: 162-7, 2015 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-25460702

RESUMO

In this work, rare earth (RE) ion RE(3+) (RE(3+)=Dy(3+), Ho(3+) and Er(3+)) doped and undoped In2O3 nanotubes are synthesized by the electrospinning method and the band gap of In2O3 is systemically controlled, depending on the order of doped elements. Dye-sensitized solar cells (DSSCs) based on In2O3:RE(3+) nanotubes are also fabricated, and significantly improved performance of In2O3-DSSC is observed due to the modulation of the band gap, larger recombination charge transfer resistance and longer electron lifetime.

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