| 1. |
- Zheng, Qian, et al.
(författare)
-
Constructing InP/ZnSe Quantum Dots with Shell Gradient In3+ Doping for Photoelectrochemical Cells
- 2024
-
Ingår i: ACS Energy Letters. - 2380-8195. ; 9:5, s. 2358-2366
-
Tidskriftsartikel (refereegranskat)abstract
- Environmentally friendly InP/ZnSe core/shell quantum dots (QDs) with high absorption coefficients and tunable band gaps have demonstrated great potential for photoelectrochemical (PEC) water splitting. However, the tightly bound excitonic feature by inherent type I band alignment tends to reduce the charge separation efficiency, limiting their PEC performance. Herein, we devised heterovalent In3+ gradient doping in the ZnSe shell of InP QD to construct core/shell structural InP/ZnSe-G-In QDs. The In3+ dopant increased the Fermi level of the ZnSe shell; thus continuous semiconductor homojunction and band bending were formed by gradient composition doping, which accelerates the exciton separation through the built-in electric field. As a result, the PEC cells based on such QDs exhibited high photocurrent density of 8.7 mA/cm2, demonstrating one of the highest values for the InP-based QDs PEC cells. This work provides an effective strategy for the application of type I band structure QDs in solar energy conversion.
|
|
| 2. |
- Akhtar, Farid, et al.
(författare)
-
Effect of WC particle size on the microstructure, mechanical properties and fracture behavior of WC--(W, Ti, Ta) C--6wt% Co cemented carbides
- 2007
-
Ingår i: International journal of refractory metals & hard materials. - : Elsevier BV. - 0263-4368. ; 25:5-6, s. 405-410
-
Tidskriftsartikel (refereegranskat)abstract
- This study deals with the microstructure and mechanical properties of WC–(W, Ti, Ta) C–9 vol.% Co cemented carbides fabricated by conventional sintering. The conventional WC particles of 4 μm size and ultrafine particles of 0.2 μm were introduced in the system with varying ratio. The ratios of conventional WC particles to ultrafine WC particles were 2:1, 1:1, and 1:2. The microstructures of sintered WC–(W, Ti, Ta) C–9 vol.% Co cemented carbides were sensitively dependent on the ratio of conventional WC particles to ultrafine WC particles. The rim phase increased with the increase in the amount of ultrafine particles. Hardness of WC–(W, Ti, Ta) C–9 vol.% Co cemented carbide increased with increase in the amount of rim phase and decrease in the average grain size of WC particles. The bending strength showed the similar trend of the hardness. The fracture morphologies are reported. The fracture behavior changed from mixed mode to transgranular fracture mode, when the ratio of conventional WC particles to ultrafine WC particles was changed from 2:1 to 1:2.
|
|
| 3. |
- Akhtar, Farid, et al.
(författare)
-
Microstructure and property evolution during the sintering of stainless steel alloy with Si 3 N 4
- 2008
-
Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 472:1-2, s. 324-331
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the sintering of a martensitic stainless steel alloy with addition of Si3N4. Sintering behavior was studied at different sintering temperatures ranging from 1250 to 1400 °C with different holding times (20–80 min) and with varying Si3N4. Results showed that the samples were densified rapidly via liquid phase sintering mechanism. Nearly full density was obtained at 1300 °C after 60 min of holding time with 5 wt% Si3N4. Temperature above 1350 °C and Si3N4 content 10 wt% caused slumping of the samples. Two weight percent Si3N4 was found chemically stable in steel alloy. Above 2 wt% Si3N4 dissolved in the steel matrix. The distribution of dissolved Si and N was characterized by XMAP. When N content reached much above its solubility limit in steel alloy it diffused out leaving pores in steel alloy with considerable decrease in the sintered density. The mechanical properties of the sintered product with varying Si3N4 were measured. A maximum ultimate tensile strength of 1011 MPa was achieved with 2 wt% Si3N4 sintered at 1300 °C after 60 min of holding time. Fracture morphologies of tensile samples are also reported.
|
|
| 4. |
- Akhtar, Farid, et al.
(författare)
-
Sintering behavior, microstructure and properties of TiC-FeCr hard alloy
- 2007
-
Ingår i: Journal of University of Science and Technology Beijing, Mineral, Metallurgy, Material. ; 14:1, s. 89-93
-
Tidskriftsartikel (refereegranskat)abstract
- TiC based cermets were produced with FeCr, as a binder, by conventional P/M (powder metallurgy) to near >97% of the theoretical density. Sintering temperature significantly affects the mechanical properties of the composite. The sintering temperature of >1360°C caused severe chemical reaction between TiC particles and the binder phase. In the TiC-FeCr cermets, the mechanical properties did not vary linearly with the carbide content. Optimum mechanical properties were found in the composite containing 57wt% TiC reinforcement, when sintered at 1360°C for 1 h. Use of carbon as an additive enhanced the mechanical properties of the composites. Cermets containing carbon as an additive with 49wt% TiC exhibited attractive mechanical properties. The microstructure of the developed composite contained less or no debonding, representing good wettability of the binder with TiC particles. Homogeneous distribution of the TiC particles ensured the presence of isotropic mechanical properties and homogeneous distribution of stresses in the composite. Preliminary experiments for evaluation of the oxidation resistance of FeCr bonded TiC cermets indicate that they are more resistant than WC-Co hardmetals
|
|
| 5. |
- Bi, Chenghao, et al.
(författare)
-
Spontaneous Self-Assembly of Cesium Lead Halide Perovskite Nanoplatelets into Cuboid Crystals with High Intensity Blue Emission
- 2019
-
Ingår i: Advanced Science. - : Wiley. - 2198-3844. ; 6:13
-
Tidskriftsartikel (refereegranskat)abstract
- Colloidal all-inorganic perovskite nanocrystals have gained significant attention as a promising material for both fundamental and applied research due to their excellent emission properties. However, reported photoluminescence quantum yields (PL QYs) of blue-emitting perovskite nanocrystals are rather low, mostly due to the fact that the high energy excitons for such wide bandgap materials are easily captured by interband traps, and then decay nonradiatively. In this work, it is demonstrated how to tackle this issue, performing self-assembly of 2D perovskite nanoplatelets into larger size (≈50 nm × 50 nm × 20 nm) cuboid crystals. In these structures, 2D nanoplatelets being isolated from each other within the cuboidal scaffold by organic ligands constitute multiple quantum wells, where exciton localization on potential disorder sites helps them to bypass nonradiative channels present in other platelets. As a result, the cuboid crystals show an extremely high PL QY of 91% of the emission band centered at 480 nm. Moreover, using the same synthetic method, mixed-anion CsPb(Br/Cl) 3 cuboid crystals with blue emission peaks ranging from 452 to 470 nm, and still high PL QYs in the range of 72–83% are produced.
|
|
| 6. |
- Bi, Chenghao, et al.
(författare)
-
Stable CsPb1- xZn xI3Colloidal Quantum Dots with Ultralow Density of Trap States for High-Performance Solar Cells
- 2020
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 32:14, s. 6105-6113
-
Tidskriftsartikel (refereegranskat)abstract
- All inorganic halide perovskites in the form of colloidal quantum dots (QDs) have come into people's view as one of the potential materials for the high-efficiency solar cells; nevertheless, the high surface trap density and poor stability of QDs restrict the performance improvement and application. Here, we obtain colloidal inorganic perovskite CsPb1-xZnxI3 QDs by the hot-injection synthesis process with the addition of ZnCl2. Synchrotron-based X-ray absorption fine structures demonstrate that the guest Zn2+ ions are doped into the CsPbI3 structure to improve the local ordering of the lattice of the perovskite, reducing the octahedral distortions. The increase of the Goldschmidt tolerance factor and the Pb-I bond energy also enhance the stability of the perovskite structure. Furthermore, the Cl- ions from ZnCl2 occupy the iodide vacancies of the perovskite to decrease the nonradiative recombination. The synergistic effect of doping and defect passivation makes for stable colloidal CsPb0.97Zn0.03I3 QDs with ultralow density of trap states. The champion solar cell based on the QDs shows a power conversion efficiency of 14.8% and a largely improved stability under ambient conditions.
|
|
| 7. |
- Brunova, Alica, et al.
(författare)
-
Structural and Trap-State Density Enhancement in Flash Infrared Annealed Perovskite Layers
- 2021
-
Ingår i: Advanced Materials Interfaces. - : WILEY. - 2196-7350. ; 8:14
-
Tidskriftsartikel (refereegranskat)abstract
- Perovskite solar cells are well-known for their high energy conversion efficiency, low-temperature processing, and cost-effective production. Flash infrared annealing (FIRA) of slot-die cast perovskite precursors offers an attractive manufacturing route using high-throughput roll-to-roll technology. Despite the recent progress in FIRA perovskite annealing, the optimal composition of the perovskite precursor is yet to be developed. Here, the effect of methylammonium chloride (MACI) on the perovskite structure and trap-state density as a function ofthe FIRA annealing time is investigated. In situ real-time grazingincidence wide-angle X-ray scattering (GIWAXS) is employed to monitor the perovskite layer formation during FIRA annealing with millisecond temporal resolution. In addition, the density of states in the bandgap is estimated using ex situ energy-resolved electrochemical impedance spectroscopy. Evidence is found that adding 10% MACI into the perovskite precursor solution significantly improves the crystallographic orientation of the perovskite layers while reducing the trap-state density by one order of magnitude. In addition, using time-resolved GIWAXS, the most favorable time window for the FIRA processing of perovskite films with the lowest mosaicity and trap-state density is identified. The results are of general importance for elucidating the appropriate temporal windows in complex and fast-evolving crystallization processes.
|
|
| 8. |
- Cao, Kequan, et al.
(författare)
-
Constructing ZnTe Spherical Quantum Well for Efficient Light Emission
- 2024
-
Ingår i: Nano Letters. - 1530-6984.
-
Tidskriftsartikel (refereegranskat)abstract
- ZnTe colloidal semiconductor nanocrystals (NCs) have shown promise for light-emitting diodes (LEDs) and displays, because they are free from toxic heavy metals (Cd). However, so far, their low photoluminescence (PL) efficiency (∼30%) has hindered their applications. Herein, we devised a novel structure of ZnTe NCs with the configuration of ZnSe (core)/ZnTe (spherical quantum well, SQW)/ZnSe (shell). The inner layer ZnTe was grown at the surface of ZnSe core with avoiding using highly active and high-risk Zn sources. Due to the formation of coherently strained heterostructure which reduced the lattice mismatch, and the thermodynamic growth of ZnTe, the surface or interface defects were suppressed. A high PL efficiency of >60% was obtained for the green light-emitting ZnSe/ZnTe/ZnSe SQWs after ZnS outer layer passivation, which is the highest value for colloidal ZnTe-based NCs. This work paves the way for the development of novel semiconductor NCs for luminescent and display applications.
|
|
| 9. |
- Cheng, Chunyan, et al.
(författare)
-
Near-Unity Quantum Yield ZnSeTe Quantum Dots Enabled by Controlling Shell Growth for Efficient Deep-Blue Light-Emitting Diodes
-
Ingår i: Advanced Functional Materials. - 1616-301X.
-
Tidskriftsartikel (refereegranskat)abstract
- Core–shell structural ZnSeTe/ZnSe/ZnS quantum dots (QDs) have attracted great attention for advanced illumination and displays because of their environmentally friendly composition, but still suffering from poor photoluminescence (PL) and electroluminescence (EL) performance due to severe non-radiative charge recombination. Herein, a stepwise injection shell growth process to manipulate the monomer concentration and ensure adequate growth interval is devised, which enables the controllable uniform epitaxial growth of ZnSe and ZnS shells on the ZnSeTe core, thus relieving the lattice distortion and defects to greatly suppress the non-radiative charge recombination. The ZnSeTe/ZnSe/ZnS QDs presented deep-blue emission at 448 nm with narrow full width at half maximum (FWHM, 23 nm), and near-unity PL quantum yield (PLQY, ≈100%) The light-emitting diodes (LEDs) based on the QDs exhibited a high external quantum efficiency (EQE) of 10.9%, a maximum brightness of 10240 cd cm−2, and a high current efficiency of 7.9 cd A−1, demonstrating a good performance for deep blue QDs LEDs (QLEDs) This shell growth strategy will be an effective approach to achieving efficient QDs and QLEDs.
|
|
| 10. |
- Deng, Min, et al.
(författare)
-
Genome-wide association analyses in Han Chinese identify two new susceptibility loci for amyotrophic lateral sclerosis
- 2013
-
Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 45:6, s. 697-
-
Tidskriftsartikel (refereegranskat)abstract
- To identify susceptibility genes for amyotrophic lateral sclerosis (ALS), we conducted a genome-wide association study (GWAS) in 506 individuals with sporadic ALS and 1,859 controls of Han Chinese ancestry. Ninety top SNPs suggested by the current GWAS and 6 SNPs identified by previous GWAS were analyzed in an independent cohort of 706 individuals with ALS and 1,777 controls of Han Chinese ancestry. We discovered two new susceptibility loci for ALS at 1q32 (CAMK1G, rs6703183, P-combined = 2.92 x 10(-8), odds ratio (OR) = 1.31) and 22p11 (CABIN1 and SUSD2, rs8141797, P-combined = 2.35 x 10(-9), OR = 1.52). These two loci explain 12.48% of the overall variance in disease risk in the Han Chinese population. We found no association evidence for the previously reported loci in the Han Chinese population, suggesting genetic heterogeneity of disease susceptibility for ALS between ancestry groups. Our study identifies two new susceptibility loci and suggests new pathogenic mechanisms of ALS.
|
|
