| 1. |
- Fan, Qunping, 1989, et al.
(author)
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Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation
- 2020
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In: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 13:12, s. 5017-5027
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Journal article (peer-reviewed)abstract
- Obtaining both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) has been a major challenge for efficient all-polymer solar cells (all-PSCs). Herein, we developed a polymer acceptor PF5-Y5 with excellent optical absorption capability (onset extending to similar to 880 nm and maximum absorption coefficient exceeding 105 cm(-1) in a film), high electron mobility (3.18 x 10(3) cm(2) V-1 s(-1)) and high LUMO level (-3.84 eV) to address such a challenge. As a result, the PBDB-T:PF5-Y5-based all-PSCs achieved a high power conversion efficiency of up to 14.45% with both a high Voc (0.946 V) and a high Jsc (20.65 mA cm(-2)), due to the high and broad absorption coverage, small energy loss (0.57 eV) and efficient charge separation and transport in the device, which are among the best values in the all-PSC field. In addition, the all-PSC shows a similar to 15% improvement in PCE compared to its counterpart small molecule acceptor (Y5)-based device. Our results suggest that PF5-Y5 is a very promising polymer acceptor candidate for applications in efficient all-PSCs.
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| 2. |
- Jensen, D. Juul, et al.
(author)
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Importance of local structural variations on recrystallization
- 2013
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In: Material Science Forum. - : Trans Tech Publications Inc.. - 9783037856888 ; , s. 37-41
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Conference paper (peer-reviewed)abstract
- Effects of local variations in the deformation microstructure on subsequent recrystallization are discussed and illustrated by three examples. The three examples consider local variations on different length scales and are: 1. Effects of local variations in the deformation microstructure on the formation of protrusions on migrating boundaries. 2. Effects of an inhomogeneous spatial distribution of second phase particles on growth. 3. Effects of stored energy and orientation variations on recrystallization kinetics.
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| 3. |
- Wu, Jingnan, 1994, et al.
(author)
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On the Conformation of Dimeric Acceptors and Their Polymer Solar Cells with Efficiency over 18 %
- 2023
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In: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 62:45
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Journal article (peer-reviewed)abstract
- The determination of molecular conformations of oligomeric acceptors (OAs) and their impact on molecular packing are crucial for understanding the photovoltaic performance of their resulting polymer solar cells (PSCs) but have not been well studied yet. Herein, we synthesized two dimeric acceptor materials, DIBP3F-Se and DIBP3F-S, which bridged two segments of Y6-derivatives by selenophene and thiophene, respectively. Theoretical simulation and experimental 1D and 2D NMR spectroscopic studies prove that both dimers exhibit O-shaped conformations other than S- or U-shaped counter-ones. Notably, this O-shaped conformation is likely governed by a distinctive "conformational lock" mechanism, arising from the intensified intramolecular & pi;-& pi; interactions among their two terminal groups within the dimers. PSCs based on DIBP3F-Se deliver a maximum efficiency of 18.09 %, outperforming DIBP3F-S-based cells (16.11 %) and ranking among the highest efficiencies for OA-based PSCs. This work demonstrates a facile method to obtain OA conformations and highlights the potential of dimeric acceptors for high-performance PSCs.
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| 4. |
- Chen, Min, et al.
(author)
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Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation
- 2019
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 10
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Journal article (peer-reviewed)abstract
- There has been an urgent need to eliminate toxic lead from the prevailing halide perovskite solar cells (PSCs), but the current lead-free PSCs are still plagued with the critical issues of low efficiency and poor stability. This is primarily due to their inadequate photovoltaic properties and chemical stability. Herein we demonstrate the use of the lead-free, all-inorganic cesium tin-germanium triiodide (CsSn(0.5)Ge(0.5)l(3)) solid-solution perovskite as the light absorber in PSCs, delivering promising efficiency of up to 7.11%. More importantly, these PSCs show very high stability, with less than 10% decay in efficiency after 500 h of continuous operation in N-2 atmosphere under one-sun illumination. The key to this striking performance of these PSCs is the formation of a full-coverage, stable native-oxide layer, which fully encapsulates and passivates the perovskite surfaces. The native-oxide passivation approach reported here represents an alternate avenue for boosting the efficiency and stability of lead-free PSCs.
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| 5. |
- Lin, Fengxiang, et al.
(author)
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Effects of structural heterogeneity of nanostructured copper on the evolution of the sizes of recrystallized grains during annealing
- 2015
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In: IOP Conference Series. - : Institute of Physics (IOP).
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Conference paper (peer-reviewed)abstract
- Recrystallization in copper deformed by dynamic plastic deformation was investigated using electron backscatter diffraction. The recrystallized grains show a broad size distribution. The kinetics of grains of different sizes is observed to be different: In the beginning of recrystallization, the area fraction of small recrystallized grains increases rapidly. At later stages of recrystallization, the area fraction of small recrystallized grains is stable, while the area fractions of medium and large recrystallized grains increase. Correlation between the broad grain size distribution (and its evolution) and the heterogeneous deformed microstructure is discussed. © Published under licence by IOP Publishing Ltd.
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| 6. |
- Lin, Fengxiang, et al.
(author)
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Importance of Non-uniform Boundary Migration for Recrystallization Kinetics
- 2018
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In: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 49:11, s. 5246-5258
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Journal article (peer-reviewed)abstract
- Recrystallization kinetics is studied by three characterization methods: post-mortem electron microscopy, in situ three-dimensional X-ray diffraction (3DXRD), and ex situ electron microscopy. Cold-rolled copper is used as a model material. The post-mortem analysis shows that the average migration velocity of unimpinged recrystallizing boundaries decreases strongly with annealing time, leading to a low Avrami exponent. For individual grains, the in situ 3DXRD measurement reveals that the growth rates decrease significantly shortly after nucleation. This is explained by the ex situ characterizations, which show that different segments of the recrystallizing boundaries migrate with significantly different velocities, and some boundaries, although unimpinged, remain stationary. This non-uniform migration of recrystallizing boundaries leads to an amoeba-like growth, and is proposed to be responsible for the decrease of the average boundary migration velocity, because the fraction of slowly moving/stationary boundaries increases during the recrystallization. Reasons for stationary boundaries are discussed based on a quantitative analysis of the local deformed microstructure. It is concluded that non-uniform boundary migration has a significant influence on recrystallization kinetics and needs to be included in recrystallization models. © 2018, The Minerals, Metals & Materials Society and ASM International.
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| 7. |
- Lin, Fengxiang, et al.
(author)
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Local strain distributions in partially recrystallized copper determined by in situ tensile investigation
- 2015
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In: IOP Conference Series. - : Institute of Physics Publishing (IOPP).
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Conference paper (peer-reviewed)abstract
- A partially recrystallized copper sample produced by cold-rolling and annealing was deformed in situ by uniaxial tension in a scanning electron microscope, and electron backscatter diffraction data were collected before and after deformation to certain strains. The local strain distributions are quantified using digital image correlation. Distributions of the normal strain along the tensile direction (εxx) are shown in this paper. The recrystallized grains are found to deform more than the remaining unrecrystallized matrix. When εxx is averaged along lines perpendicular to the tensile direction, significant variation are observed, which may be related to the local recrystallized volume fraction. © Published under licence by IOP Publishing Ltd.
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| 8. |
- Lin, Fengxiang, et al.
(author)
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Supercube grains leading to a strong cube texture and a broad grain size distribution after recrystallization
- 2015
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In: Philosophical Magazine. - : Taylor & Francis. - 1478-6435 .- 1478-6443. ; 95:22, s. 2427-2449
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Journal article (peer-reviewed)abstract
- This work revisits the classical subject of recrystallization of cold-rolled copper. Two characterization techniques are combined: three-dimensional X-ray diffraction using synchrotron X-rays, which is used to measure the growth kinetics of individual grains in situ, and electron backscatter diffraction, which is used for statistical analysis of the microstructural evolution. As the most striking result, the strong cube texture after recrystallization is found to be related to a few super large cube grains, which were named supercube grains. These few supercube grains become large due to higher growth rates. However, most other cube grains do not grow preferentially. Because of the few supercube grains, the grain size distribution after recrystallization is broad. Reasons for the higher growth rates of supercube grains are discussed, and are related to the local deformed microstructure. © 2015 Taylor & Francis.
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| 9. |
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| 10. |
- Salvati, E., et al.
(author)
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Nanoscale structural damage due to focused ion beam milling of silicon with Ga-ions
- 2018
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In: Materials letters (General ed.). - : Elsevier. - 0167-577X .- 1873-4979. ; 213, s. 346-349
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Journal article (peer-reviewed)abstract
- The exposure of sample to Focused Ion Beam leads to Ga-ion implantation, damage, material amorphisation, and the introduction of sources of residual stress; namely eigenstrain. In this study we employ synchrotron X-ray Reflectivity technique to characterise the amorphous layer generated in a single crystal Silicon sample by exposure to Ga-ion beam. The thickness, density and interface roughness of the amorphous layer were extracted from the analysis of the reflectivity curve. The outcome is compared with the eigenstrain profile evaluated from residual stress analysis by Molecular Dynamics and TEM imaging reported in the literature. (c) 2017 Elsevier B.V. All rights reserved.
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