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| 2. |
- Cai, Yunhao, et al.
(författare)
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Effect of the Energy Offset on the Charge Dynamics in Nonfullerene Organic Solar Cells
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:39, s. 43984-43991
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Tidskriftsartikel (refereegranskat)abstract
- The energy offset, considered as the driving force for charge transfer between organic molecules, has significant effects on both charge separation and charge recombination in organic solar cells. Herein, we designed material systems with gradually shifting energy offsets, including both positive and negative values. Time-resolved spectroscopy was used to monitor the charge dynamics within the bulk heterojunction. It is striking to find that there is still charge transfer and charge generation when the energy offset reached -0.10 eV (ultraviolet photoelectron spectroscopy data). This work not only indicates the feasibility of the free carrier generation and the following charge separation under the condition of a negative offset but also elucidates the relationship between the charge transfer and the energy offset in the case of polymer chlorination.
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| 3. |
- Li, Chao, et al.
(författare)
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Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells
- 2021
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Ingår i: Nature Energy. - : NATURE RESEARCH. - 2058-7546.
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Tidskriftsartikel (refereegranskat)abstract
- Molecular design of acceptor and donor molecules has enabled major progress in organic photovoltaics. Li et al. show that branched alkyl chains in non-fullerene acceptors allow favourable morphology in the active layer, enabling a certified device efficiency of 17.9%. Molecular design of non-fullerene acceptors is of vital importance for high-efficiency organic solar cells. The branched alkyl chain modification is often regarded as a counter-intuitive approach, as it may introduce an undesirable steric hindrance that reduces charge transport in non-fullerene acceptors. Here we show the design and synthesis of a highly efficient non-fullerene acceptor family by substituting the beta position of the thiophene unit on a Y6-based dithienothiophen[3,2-b]-pyrrolobenzothiadiazole core with branched alkyl chains. It was found that such a modification to a different alkyl chain length could completely change the molecular packing behaviour of non-fullerene acceptors, leading to improved structural order and charge transport in thin films. An unprecedented efficiency of 18.32% (certified value of 17.9%) with a fill factor of 81.5% is achieved for single-junction organic solar cells. This work reveals the importance of the branched alkyl chain topology in tuning the molecular packing and blend morphology, which leads to improved organic photovoltaic performance.
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| 4. |
- Ai, Songyuan, et al.
(författare)
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Ab Initio Calculations on Elastic Properties of IF Steel Matrix Phase at High Temperature Based on Lattice Expansion Theory
- 2020
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- Elucidating the evolution law of the elastic properties of the matrix phase is of great significance for the control of steel properties and quality during continuous casting and subsequent heat treatment. In this paper, thermal expansion experiments and ab initio calculations are used to study the elastic properties of the interstitial free (IF) steel matrix phase in different magnetic states and crystal structures. The results show that the bulk modulus B and the tetragonal shear elastic constant C' for the entire temperature range decrease with increasing temperature, but C-44 is the opposite. While from paramagnetic (PM) to ferromagnetic (FM) state, C'(C-44) have changed similar to 188% (similar to 27%), B increases by similar to 55% during the crystal structure change (fcc -> bcc). With the FM to PM state, the Zener anisotropy parameter increases sharply, and Young's modulus decreases significantly in the [001] direction; the maximum difference is similar to 76 GPa. The evolution rate of average Young's modulus in single bcc-phase FM (fcc-phase PM) range reaches similar to 5.5(similar to 5.6) x 10(-2) GPa K-1. The research provides an effective method for ab initio calculation of the elastic properties of interstitial free and ultra-low carbon steels at high temperature, also furnishing a basis for the application of ab initio calculations to the high temperature performance of steel materials.
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| 5. |
- Lin, Yuze, et al.
(författare)
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Mapping Polymer Donors toward High-Efficiency Fullerene Free Organic Solar Cells
- 2017
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 29:3
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Tidskriftsartikel (refereegranskat)abstract
- Five polymer donors with distinct chemical structures and different electronic properties are surveyed in a planar and narrow-bandgap fused-ring electron acceptor (IDIC)-based organic solar cells, which exhibit power conversion efficiencies of up to 11%.
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| 6. |
- Menghrajani, Kamal, et al.
(författare)
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Risk classification at diagnosis predicts post-HCT outcomes in intermediate-, adverse-risk, and KMT2A-rearranged AML
- 2022
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Ingår i: Blood Advances. - : American Society of Hematology. - 2473-9529 .- 2473-9537. ; 6:3, s. 828-847
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about whether risk classification at diagnosis predicts post-hematopoietic cell transplantation (HCT) outcomes in patients with acute myeloid leukemia (AML). We evaluated 8709 patients with AML from the CIBMTR database, and after selection and manual curation of the cytogenetics data, 3779 patients in first complete remission were included in the final analysis: 2384 with intermediate-risk, 969 with adverse-risk, and 426 with KMT2A-rearranged disease. An adjusted multivariable analysis detected an increased risk of relapse for patients with KMT2A-rearranged or adverse-risk AML as compared to those with intermediate-risk disease (hazards ratio [HR], 1.27; P = .01; HR, 1.71; P < .001, respectively). Leukemia-free survival was similar for patients with KMT2A rearrangement or adverse risk (HR, 1.26; P = .002, and HR, 1.47; P < .001), as was overall survival (HR, 1.32; P < .001, and HR, 1.45; P < .001). No differences in outcome were detected when patients were stratified by KMT2A fusion partner. This study is the largest conducted to date on post-HCT outcomes in AML, with manually curated cytogenetics used for risk stratification. Our work demonstrates that risk classification at diagnosis remains predictive of post-HCT outcomes in AML. It also highlights the critical need to develop novel treatment strategies for patients with KMT2A-rearranged and adverse-risk disease.
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| 7. |
- Chen, Xian-Kai, et al.
(författare)
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A unified description of non-radiative voltage losses in organic solar cells
- 2021
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Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 6:8, s. 799-806
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Tidskriftsartikel (refereegranskat)abstract
- Organic solar cells based on non-fullerene acceptors have enabled high efficiencies yet their charge dynamics and its impact on the photovoltaic parameters are not fully understood. Now, Chen et al. provide a general description of non-radiative voltage losses in both fullerene and non-fullerene solar cells. Recent advances in organic solar cells based on non-fullerene acceptors (NFAs) come with reduced non-radiative voltage losses (Delta V-nr). Here we show that, in contrast to the energy-gap-law dependence observed in conventional donor:fullerene blends, the Delta V-nr values in state-of-the-art donor:NFA organic solar cells show no correlation with the energies of charge-transfer electronic states at donor:acceptor interfaces. By combining temperature-dependent electroluminescence experiments and dynamic vibronic simulations, we provide a unified description of Delta V-nr for both fullerene- and NFA-based devices. We highlight the critical role that the thermal population of local exciton states plays in low-Delta V-nr systems. An important finding is that the photoluminescence yield of the pristine materials defines the lower limit of Delta V-nr. We also demonstrate that the reduction in Delta V-nr (for example, <0.2 V) can be obtained without sacrificing charge generation efficiency. Our work suggests designing donor and acceptor materials with high luminescence efficiency and complementary optical absorption bands extending into the near-infrared region.
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| 8. |
- Kanchana, V., et al.
(författare)
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Lattice dynamics and elastic properties of the 4 f electron system : CeN
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:20, s. 205135-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure, structural stability, and lattice dynamics of cerium mononitride are investigated using ab initio density-functional methods involving an effective potential derived from the generalized gradient approximation and without special treatment for the 4 f states. The 4 f states are hence allowed to hop from site to site, without an on-site Hubbard U, and contribute to the bonding, in a picture often referred to as itinerant. It is argued that this picture is appropriate for CeN at low temperatures, while the anomalous thermal expansion observed at elevated temperatures indicates entropy-driven localization of the Ce f electrons, similar to the behavior of elemental cerium. The elastic constants are predicted from the total energy variation of strained crystals and are found to be large, typical for nitrides. The phonon dispersions are calculated showing no soft modes, and the Gruneisen parameter behaves smoothly. The electronic structure is also calculated using the quasiparticle self-consistent GW approximation (where G denotes the Green's function and W denotes the screened interaction). The Fermi surface of CeN is dominated by large egg-shaped electron sheets centered on the X points, which stem from the p-f mixing around the X point. In contrast, assuming localized f electrons leads to a semimetallic picture with small band overlaps around X.
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| 9. |
- Long, Jianzhan, 1979, et al.
(författare)
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Influences of Cr contents on oxidation behavior of WC-Co-Ni-Cr cemented carbides at 900 °C
- 2024
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Ingår i: International Journal of Refractory Metals and Hard Materials. - 0263-4368 .- 2213-3917. ; 118
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Tidskriftsartikel (refereegranskat)abstract
- Modification of binder composition is an effective way to improve the oxidation resistance of WC-Co-Ni-Cr cemented carbide. Since the adjustment of Ni and Cr contents in the Co-Ni-Cr binder alters the oxidation behavior and oxidation products, WC-Co-Ni-Cr cemented carbide is expected to achieve excellent oxidation resistance in severe service conditions. In this paper, the influences of Cr contents in Co-Ni-Cr binder phase with a fixed total amount of Co and Ni on the oxidation behavior of WC-Co-Ni-Cr cemented carbides at 900 °C was investigated. The oxide morphology and phase distribution were focused. The oxidation mechanism of WC-Co-Ni-Cr cemented carbide was discussed. It has been shown that Co-rich regions are preferentially oxidized in the initial stage of oxidation. As oxidation proceeds (60 min), the dominant oxidation product on the alloy surface is NiO. The oxidation resistance of the WC-Co-Ni-Cr cemented carbide increases with increasing Cr content in the binder. Compared to the series of WC-2Co-11Ni-xCr, WC-6.5Co-6.5Ni-xCr presents a better overall oxidation resistance due to the formation of Cr2O5 in the middle of the oxide layer.
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| 10. |
- Song, Jiali, et al.
(författare)
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Solid additive engineering enables high-efficiency and eco-friendly all-polymer solar cells
- 2022
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Ingår i: Matter. - : ELSEVIER. - 2590-2393 .- 2590-2385. ; 5:11, s. 4047-4059
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Tidskriftsartikel (refereegranskat)abstract
- Currently, morphology optimization of all-polymer solar cells (all-PSCs) strongly depends on the use of solvent additives, which are usually highly toxic and harmful to the environment and human health. Here, we report a green and volatile solid additive, 2-methoxynaphthalene (2-MN). It was found that the incorporation of 2-MN into a PM6:PY-DT blend can effectively manipulate the aggregations of PM6 and PY-DT during film depositing and thermal annealing processes and results in highly ordered molecular packing and favorable phase-separated morphology. Consequently, a re-cord-high efficiency of 17.32% is achieved for the PM6:PY-DT de-vice. Moreover, 2-MN-processed all-PSCs were fabricated by using non-halogenated solvent. High efficiencies of 17.03% and 16.67% are obtained for all-PSCs fabricated under nitrogen atmosphere and ambient conditions, respectively. Our work shows that the utili-zation of 2-MN as a green and solid additive is a simple and feasible strategy to optimize the morphology and sheds new light on eco-friendly fabrication and application of all-PSCs.
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