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Perovskite solar cell with an efficient TiO? compact film.
ACS Appl Mater Interfaces
PUBLISHED: 09-05-2014
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A perovskite solar cell with a thin TiO2 compact film prepared by thermal oxidation of sputtered Ti film achieved a high efficiency of 15.07%. The thin TiO2 film prepared by thermal oxidation is very dense and inhibits the recombination process at the interface. The optimum thickness of the TiO2 compact film prepared by thermal oxidation is thinner than that prepared by spin-coating method. Also, the TiO2 compact film and the TiO2 porous film can be sintered at the same time. This one-step sintering process leads to a lower dark current density, a lower series resistance, and a higher recombination resistance than those of two-step sintering. Therefore, the perovskite solar cell with the TiO2 compact film prepared by thermal oxidation has a higher short-circuit current density and a higher fill factor.
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Pt-Ni Alloy Nanoparticles as Superior Counter Electrodes for Dye-Sensitized Solar Cells: Experimental and Theoretical Understanding.
Adv. Mater. Weinheim
PUBLISHED: 08-28-2014
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Pt-Ni alloy nanoparticles are synthesized and used as counter electrodes in dye-sensitized solar cells (DSSCs) for the first time. A PCE of 9.15% is achieved with the Pt3 Ni counter electrode, displaying an evident improvement compared with the conventional pure Pt (8.33%). The cell stability is also obviously increased with the Pt3 Ni counter electrode.
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Field electron emission of layered Bi?Se? nanosheets with atom-thick sharp edges.
Nanoscale
PUBLISHED: 06-17-2014
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Field electron emission properties of solution processed few-layer Bi?Se? nanosheets are studied for the first time, which exhibit a low turn-on field of 2.3 V ?m(-1), a high field enhancement factor of up to 6860 and good field emission stability. This performance is better than that of the as reported layered MoS?f sheets and is comparable to that of single layer graphene films. The efficient field emission behaviours are found to be not only attributed to their lower work function but also related to their numerous sharp edges or protrusion decorated structure based on our simulation results. Besides, the contribution of possible two-dimensional electron gas surface states of atom-thick layered Bi?Se? nanosheets is discussed in this paper. We anticipate that these solution processed layered Bi?Se? nanosheets have great potential as robust high-performance vertical structure electron emitters for future light weight and highly flexible vacuum micro/nano-electronic device applications.
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Enhanced electroluminescence using Ta?O?/ZnO/HfO? asymmetric double heterostructure in ZnO/GaN-based light emitting diodes.
Opt Express
PUBLISHED: 06-13-2014
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ZnO/GaN-based light-emitting diodes (LEDs) with improved asymmetric double heterostructure of Ta?O?/ZnO/HfO? have been fabricated. Electroluminescence (EL) performance has been enhanced by the HfO? electron blocking layer and further improved by continuing inserting the Ta?O? hole blocking layer. The origins of the emission have been identified, which indicated that the Ta?O?/ZnO/HfO? asymmetric structure could more effectively confine carriers in the active i-ZnO layer and meanwhile suppresses of radiation from GaN. This device exhibits superior stability in long-time running. It's hoped that the asymmetric double heterostructure may be helpful for the development of the future ZnO-based LEDs.
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Unusual electroluminescence from n-ZnO@i-MgO core-shell nanowire color-tunable light-emitting diode at reverse bias.
Phys Chem Chem Phys
PUBLISHED: 04-10-2014
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Light-emitting diodes (LEDs) based on n-ZnO@i-MgO core-shell (CS) nanowires (NWs) are herein demonstrated and characterized. MgO insulating layers were rationally introduced as shells to modify/passivate the surface defects of ZnO NWs. A high-quality ZnO/MgO interface was attained and the optically pumped near-band-edge emission of the bare ZnO NWs was greatly enhanced after cladding i-MgO shells. Electroluminescence (EL) spectra measured in the whole UV-visible range revealed that light emission can only be detected when LEDs were applied with reverse bias. Moreover, the emission color can be tuned from orange to bright white with increasing reverse bias. We explored these interesting results tentatively in terms of the energy-band diagram of the heterojunction and it was found that the interfacial i-MgO shells not only acted as an insulator to prevent a short circuit between the two electrodes, but also offered a potential energy difference so that electron tunneling was energetically possible, both of which were essential to generate the reverse-bias EL. The dipole-forbidden d-d transitions by the Laporte selection rule in the p-NiO might be the reason to why there is no light being detected from the CS NW LED under forward bias. It is hoped that this simple and facile route may provide an effective approach in designing low-cost CS NW LEDs.
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In situ synthesis of NiS nanowall networks on Ni foam as a TCO-free counter electrode for dye-sensitized solar cells.
ACS Appl Mater Interfaces
PUBLISHED: 04-01-2014
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Nickel sulfide (NiS) nanowall networks have been prepared by a novel one-step hydrothermal method on a nickel (Ni) foam substrate. The Ni foam has a high conductivity and porous structure. To our knowledge, the Ni foam is used as a conductive substrate for the dye-sensitized solar cell (DSSC) for the first time. The Ni foam is used as not only the conductive substrate but also the Ni sources of the reaction. The Ni foam supported NiS prepared by this simple hydrothermal method shows high catalytic activity for reduction of triiodide ions. The DSSC with a transparent conductive oxide (TCO)-free NiS counter electrode (CE) was herein developed and showed a higher power conversion efficiency of 8.55% than that with a TCO supported NiS CE (7.47%) and a TCO supported platinum CE (7.99%).
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Sulfur-doped molybdenum oxide anode interface layer for organic solar cell application.
ACS Appl Mater Interfaces
PUBLISHED: 02-18-2014
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Efficient organic solar cells (OSCs) based on regioregular of poly (3-hexylthiophene):fullerene derivative [6,6]-phenyl-C61butyric acid methyl ester composites have been fabricated on indium tin oxide (ITO) coated glass substrates by using a sputtered sulfur-doped molybdenum oxide (S-MoO3) film as anode interface layer (AIL). With the help of X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy, we find that oxygen flow ratio control can modulate the amount of sulfur doping into MoO3, then further tune the Mo(+4)/Mo(+5)/Mo(+6) composition ratios, Fermi level, electron affinity, valence band ionization energy and band gap of MoO3. A partially occupied Mo 4d-bands of Mo(5+) and Mo(4+) states modulated by sulfur doping are the main factor which influences the valence electronic structure of S-MoO3.These orbitals overlap interrelation push the valence band close to S-MoO3's Fermi level, thus make it into a p-type semiconductor. S-MoO3 with smaller ionization energy and electron affinity is better suitable as an efficient AIL. On the basis of these AILs, a photovoltaic power conversion efficiency up to 3.69% has been achieved, which is 12% higher than that in pure MoO3 AIL case. The result thus shows that sulfur doping is a useful method to modify anode interface layer for improving the hole-transport properties of MoO3, which can improve the device performances.
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Synthesis and field emission studies of tower-like GaN nanowires.
Nanoscale Res Lett
PUBLISHED: 01-01-2014
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Tower-like GaN nanowires were successfully fabricated on Au-coated Si substrates by chemical vapor deposition. The tower-like nanowire consisted of a nanowire at the center and microcrystal layers stacked one by one around the nanowire. The tower-like nanowires grew along the [0001] direction, and the exposed surfaces of the microcrystal layers are [Formula: see text] and [Formula: see text] facets. The growth mechanism of the tower-like GaN nanowires was proposed. The field emission property of tower-like GaN nanowires was tested. Due to the sharp tips, nearly vertical alignment and rough surfaces caused by the microcrystal layers, the tower-like GaN nanowires show excellent performance in field emission with a turn-on field of 2.44 V/?m which is lower than those of other GaN one-dimensional (1D) nanomaterials.
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Vibration test method to study elastic stability of porous carbon nanocomposite counter electrode in dye sensitized solar cells.
ACS Appl Mater Interfaces
PUBLISHED: 07-22-2013
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An out-of-plane elastic vibration test method is developed to directly study the elastic stability of elastic Ti foil-supported porous carbon nanocomposite (CNC) counter electrode (CE) of dye sensitized solar cells (DSSCs). The stability of CE, estimated by that of power conversion efficiency (PCE) of the CE-based DSSC device, is studied from the views of CNC morphology, equivalent resistances, exchange current density and contact model of CE. The results suggest thinner thickness and bigger interbundling degree of CNC layer is beneficial to the total internal impedance value of CE, and then beneficial to the CE stability. With optimal CNC structure, even if the CE is springed 1000 times with max amplification about 10 mm, the PCE of CE-based DSSC can remain 80% of the initial value. The test method is interesting and the results may have a potential use for elastic stability study of general elastic devices.
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Seedless synthesis of layered ZnO nanowall networks on Al substrate for white light electroluminescence.
Nanotechnology
PUBLISHED: 07-15-2013
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In this paper, layered ZnO nanowall networks were directly grown on Al substrates using a hydrothermal method without predepositing seed layers. The individual ZnO nanowalls with a thickness of several nanometers and a size of several hundred nanometers were (002) surface dominated, in which the preferential growth direction of ZnO was suppressed. White electroluminescence devices were fabricated based on Au/polymethylmethacrylate/ZnO-nanowall (metal-insulator-semiconductor) structures. The chromaticity coordinate of the electroluminescence spectrum for the optimal device was calculated as (0.27, 0.34), which is close to (0.33, 0.33) of standard white light.
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Controllable synthesis of flake-like Al-doped ZnO nanostructures and its application in inverted organic solar cells.
Nanoscale Res Lett
PUBLISHED: 05-08-2011
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Flake-like Al-doped ZnO (AZO) nanostructures including dense AZO nanorods were obtained via a low-temperature (100°C) hydrothermal process. By doping and varying Al concentrations, the electrical conductivity (?) and morphology of the AZO nanostructures can be readily controlled. The effect of ? and morphology of the AZO nanostructures on the performance of the inverted organic solar cells (IOSCs) was studied. It presents that the optimized power conversion efficiency of the AZO-based IOSCs is improved by approximately 58.7% compared with that of un-doped ZnO-based IOSCs. This is attributed to that the flake-like AZO nanostructures of high ? and tunable morphology not only provide a high-conduction pathway to facilitate electron transport but also lead to a large interfacial area for exciton dissociation and charge collection by electrodes.
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Ultraviolet photodetectors based on ZnO nanorods-seed layer effect and metal oxide modifying layer effect.
Nanoscale Res Lett
PUBLISHED: 02-15-2011
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Pt/ZnO nanorod (NR) and Pt/modified ZnO NR Schottky barrier ultraviolet (UV) photodetectors (PDs) were prepared with different seed layers and metal oxide modifying layer materials. In this paper, we discussed the effect of metal oxide modifying layer on the performance of UV PDs pre- and post-deposition annealing at 300°C, respectively. For Schottky barrier UV PDs with different seed layers, the MgZnO seed layer-PDs without metal oxide coating showed bigger responsivity and larger detectivity (D?*) than those of PDs with ZnO seed layer, and the reason was illustrated through energy band theory and the electron transport mechanism. Also the ratio of D254* to D546* was calculated above 8 × 102 for all PDs, which demonstrated that our PDs showed high selectivity for detecting UV light with less influence of light with long wavelength.
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Thickness dependence of the MoO(3) blocking layers on ZnO nanorod-inverted organic photovoltaic devices.
Appl Phys Lett
PUBLISHED: 01-20-2011
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Organic solar cells based on vertically aligned zinc oxide nanorod arrays (ZNR) in an inverted structure of indium tin oxide (ITO)?ZNR?poly(3-hexylthiophene): (6,6)-phenyl C61 butyric acid methyl ester(P3HT:PCBM)?MoO(3)?aluminum(Al) were studied. We found that the optimum MoO(3) layer thickness condition of 20 nm, the MoO(3) can effectively decrease the probability of bimolecular recombination either at the Al interface or within the active layer itself. For this optimum condition we get a power conversion efficiency of 2.15%, a short-circuit current density of 9.02 mA?cm(2), an open-circuit voltage of 0.55V, and a fill factor of 0.44 under 100 mW?cm(2) irradiation. Our investigations also show that the highly crystallized ZNR can create short and continuous pathways for electron transport and increase the contact area between the ZNR and the organic materials.
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High optical switching speed and flexible electrochromic display based on WO3 nanoparticles with ZnO nanorod arrays supported electrode.
Nanotechnology
PUBLISHED: 04-14-2009
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The electrochromic (EC) property of WO(3) nanoparticles grown on vertically self-aligned ZnO nanorods (ZNRs) is reported. An electrochromic character display based on WO(3) nanoparticle-modified ZnO nanorod arrays on a flexible substrate has been fabricated and demonstrated. The ZNRs were first synthesized on ZnO-seed-coated In(2)O(3):Sn (ITO) glass (1 cm(2) cell) and polyethylene terephthalate (PET) (4 cm(2) cell) substrates by a low temperature hydrothermal method, and then amorphous WO(3) nanoparticles were grown directly on the surface of the ZNRs by the pulsed laser deposition (PLD) method. The ZNR-based EC device shows high transparence, good electrochromic stability and fast switching speed (4.2 and 4 s for coloration and bleaching, respectively, for a 1 cm(2) cell). The good performance of the ZNR electrode-based EC display can be attributed to the large surface area, high crystallinity and good electron transport properties of the ZNR arrays. Its high contrast, fast switching, good memory and flexible characteristics indicate it is a promising candidate for flexible electrochromic displays or electronic paper.
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Structural and optical characterization of ZnO/Mg(x)Zn(1-x)O multiple quantum wells based random laser diodes.
ACS Appl Mater Interfaces
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Two kinds of laser diodes (LDs) comprised of ZnO/Mg(x)Zn(1-x)O (ZnO/MZO) multiple quantum wells (MQWs) grown on GaN (MQWs/GaN) and Si (MQWs/Si) substrates, respectively, have been constructed. The LD with MQWs/GaN exhibits ultraviolet random lasing under electrical excitation, while that with MQWs/Si does not. In the MQWs/Si, ZnO/MZO MQWs consist of nanoscaled crystallites, and the MZO layers undergo a phase separation of cubic MgO and hexagonal ZnO. Moreover, the Mg atom predominantly locates in the MZO layers along with a significant aggregation at the ZnO/MZO interfaces; in sharp contrast, the ZnO/MZO MQWs in the MQWs/GaN show a well-crystallized structure with epitaxial relationships among GaN, MZO, and ZnO. Notably, Mg is observed to diffuse into the ZnO well layers. The structure-optical property relationship of these two LDs is further discussed.
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Nanointerlayer induced electroluminescence transition from ultraviolet- to red-dominant mode for n-Mn:ZnO/N-GaN heterojunction.
ACS Appl Mater Interfaces
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High-quality Mn:ZnO (MZO) film had been prepared on N-GaN coated sapphire substrates followed by postdeposition thermal annealing treatment at 700 °C. For the annealed MZO/GaN heterojunction, a 15 nm cubic structural ZnGa(2)O(4) layer was observed at the MZO/GaN interface through transmission electron microscope analysis. Through electroluminescence (EL) measurement, the formation of the nanointerface results in an EL transition from ultraviolet- to red-dominant mode for n-Mn:ZnO/N-GaN heterojunction light-emitting diodes (LEDs). The heterojunction LED showed a rectification ratio of ?2.0 × 10(5) at ±2 V, a dark current of 3.5 nA at -2 V and a quite strong red EL with a low turn-on voltage of 3 V. On the basis of the energy band diagram, we think the EL transition from ultraviolet- to red-dominant mode is mainly due to the formation of a thin oxide blocking nanolayer at the MZO/GaN interface during the annealing process.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.