| 1. |
- Lin, Baojun, et al.
(författare)
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Balancing the pre-aggregation and crystallization kinetics enables high efficiency slot-die coated organic solar cells with reduced non-radiative recombination losses
- 2020
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 13:8, s. 2467-2479
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Tidskriftsartikel (refereegranskat)abstract
- Slot-die coating being compatible with the roll-to-roll technique has been regarded as a promising tool for upscaling the manufacturing of organic solar cells (OSCs). However, there has been a significant gap between the efficiencies of the state-of-the-art spin-coated devices and the scalable processed devices. The active layer morphology is crucial to achieve high efficiency in OSCs, which depends on the conditions of film fabrication. To figure out and optimize the slot-die coating process, a deeper understanding of the film formation kinetics is important. Herein, in situ measurements of the slot-die coating process based on the PM7:IT4F system are demonstrated to illustrate the aggregation and crystallization evolution at various die temperatures and substrate temperatures. OSCs with a high power conversion efficiency of 13.2% are achieved at 60 degrees C die temperature/60 degrees C substrate temperature due to the improved exciton dissociation, charge transport and suppressed non-radiative charge recombination. The optimized morphology is attributed to the balanced polymer pre-aggregation and small molecule crystallization kinetics. The unsuitable die temperature leads to overlarge phase separation and consequently inefficient exciton dissociation while the improper substrate temperature results in weak crystallization and the following shrunken carrier lifetime with strong non-radiative combination. This work provides fundamental understanding on the correlations among processing methodology, solution pre-aggregation, morphology formation kinetics, device physics and device performance and affords guidance for device optimization in scalable manufacturing.
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| 2. |
- Xu, Xiaofeng, et al.
(författare)
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Large-Area, Semitransparent, and Flexible All-Polymer Photodetectors
- 2018
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 28:48
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Tidskriftsartikel (refereegranskat)abstract
- Photodetectors, converting optical signals from specific wavelengths to electrical signals, have many applications on photoimaging, optical communication, and environmental monitoring. Solution-processed organic photodetectors (OPDs) based on organic materials emerge promise especially for wearable electronics and smart buildings. In this work, new all-polymer photodetectors (all-PPDs) are developed based on bulk-heterojunction active layers which incorporate a donor polymer and an acceptor polymer. The inverted all-PPDs exhibit outstanding external quantum efficiency over 70%, low dark current density (J(d)) of 1.1 x 10(-8) A cm(-2), and high detectivity (D*) over 3.0 x 10(12) Jones with planar response over the entire visible range. It is one of the best-performing all-PPDs reported so far and is also comparable with many organic and inorganic photodetectors. By using lamination technique, large-area, semitransparent, flexible, and "fully" polymeric photodetectors are successfully fabricated for the first time, with D* over 10(11) Jones for double-side light detection. The results highlight the great potential for producing high-performance all-PPDs by taking advantages of various device architecture and solution-processing techniques.
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| 3. |
- Zhou, Ke, et al.
(författare)
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Molecular Orientation of Polymer Acceptor Dominates Open-Circuit Voltage Losses in All-Polymer Solar Cells
- 2019
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Ingår i: ACS Energy Letters. - : AMER CHEMICAL SOC. - 2380-8195. ; 4:5, s. 1057-1064
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Tidskriftsartikel (refereegranskat)abstract
- Low open-circuit voltage (V-oc) induced by energy loss in organic solar cells is considered to be one of the most influencing factors limiting device performance, in which morphology of the active layer plays a crucial role in determining energy loss. By employing a bilayer structure of the P3HT:N2200 all-polymer system, we have identified the isolated impact of a molecular packing structure on device V-oc with analysis of energy loss processes. Thermal annealing and various solvents were used to control molecular orientation in P3HT:N2200 bilayer devices, in which different V-oc spanning from 0.45 to 0.54 V could be obtained. It was found that energy of charge-transfer state (E-ct) differed in these bilayer devices. Besides, increased charge recombination could be observed in bilayer devices when N2200 layers exhibited face-on orientation, which caused an additional energy loss and decreased V-oc. Our results suggest that rational control of polymer molecular orientation is essential to reduce the energy loss and ultimately achieve high V-oc in all-polymer solar cells.
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| 4. |
- Zhou, Ke, et al.
(författare)
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pi-pi Stacking Distance and Phase Separation Controlled Efficiency in Stable All-Polymer Solar Cells
- 2019
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- The morphology of the active layer plays a crucial role in determining device performance and stability for organic solar cells. All-polymer solar cells (All-PSCs), showing robust and stable morphologies, have been proven to give better thermal stability than their fullerene counterparts. However, outstanding thermal stability is not always the case for polymer blends, and the limiting factors responsible for the poor thermal stability in some All-PSCs, and how to obtain higher efficiency without losing stability, still remain unclear. By studying the morphology of poly [2,3-bis (3-octyloxyphenyl) quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl](TQ1)/poly[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b ]dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]] (PCE10)/PNDI-T10 blend systems, we found that the rearranged molecular packing structure and phase separation were mainly responsible for the poor thermal stability in devices containing PCE10. The TQ1/PNDI-T10 devices exhibited an improved PCE with a decreased pi-pi stacking distance after thermal annealing; PCE10/PNDI-T10 devices showed a better pristine PCE, however, thermal annealing induced the increased pi-pi stacking distance and thus inferior hole conductivity, leading to a decreased PCE. Thus, a maximum PCE could be achieved in a TQ1/PCE10/PNDI-T10 (1/1/1) ternary system after thermal annealing resulting from their favorable molecular interaction and the trade-off of molecular packing structure variations between TQ1 and PCE10. This indicates that a route to efficient and thermal stable All-PSCs can be achieved in a ternary blend by using material with excellent pristine efficiency, combined with another material showing improved efficiency under thermal annealing.
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| 5. |
- Beck, Dominik, et al.
(författare)
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Integrative analysis of next generation sequencing for small non-coding RNAs and transcriptional regulation in Myelodysplastic Syndromes
- 2011
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Ingår i: BMC Medical Genomics. - : Springer Science and Business Media LLC. - 1755-8794. ; 4:19, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundMyelodysplastic Syndromes (MDSS) are pre-leukemic disorders with increasing incident rates worldwide, but very limited treatment options. Little is known about small regulatory RNAs and how they contribute to pathogenesis, progression and transcriptome changes in MDS.MethodsPatients' primary marrow cells were screened for short RNAs (RNA-seq) using next generation sequencing. Exon arrays from the same cells were used to profile gene expression and additional measures on 98 patients obtained. Integrative bioinformatics algorithms were proposed, and pathway and ontology analysis performed.ResultsIn low-grade MDS, observations implied extensive post-transcriptional regulation via microRNAs (miRNA) and the recently discovered Piwi interacting RNAs (piRNA). Large expression differences were found for MDS-associated and novel miRNAs, including 48 sequences matching to miRNA star (miRNA*) motifs. The detected species were predicted to regulate disease stage specific molecular functions and pathways, including apoptosis and response to DNA damage. In high-grade MDS, results suggested extensive post-translation editing via transfer RNAs (tRNAs), providing a potential link for reduced apoptosis, a hallmark for this disease stage. Bioinformatics analysis confirmed important regulatory roles for MDS linked miRNAs and TFs, and strengthened the biological significance of miRNA*. The "RNA polymerase II promoters" were identified as the tightest controlled biological function. We suggest their control by a miRNA dominated feedback loop, which might be linked to the dramatically different miRNA amounts seen between low and high-grade MDS.DiscussionThe presented results provide novel findings that build a basis of further investigations of diagnostic biomarkers, targeted therapies and studies on MDS pathogenesis.
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| 6. |
- Jin, Yunzhe, et al.
(författare)
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Effects of in-situ stress on heat transfer in fracture networks
- 2024
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Ingår i: Geomechanics for Energy and the Environment. - : Elsevier BV. - 2352-3808. ; 37
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Tidskriftsartikel (refereegranskat)abstract
- Stress-induced fracture deformation is the principal cause for permeability change in geothermal systems. This study focuses on the influence of the nonlinear deformation and dilation effect of fractures on the geothermal system under the action of in-situ stress. By adopting a nonlinear constitutive model of rock fractures and embedding discrete fracture networks, numerical studies are first conducted to investigate the effects of different in-situ stress schemes on fracture aperture evolution using a rigid-body spring method. Based on the anisotropic aperture field of the fracture network caused by the in-situ stress, a finite element method is then used to study the flow and heat transfer process. The effects of different stress schemes on the heat flow transfer process are analyzed. Numerical simulation results show that when the ratio of horizontal to vertical stresses is not sufficient to cause shear dilation effects, the nonlinear normal deformation is the main factor affecting flow and heat transfer. In this case, the heat extraction efficiency is reduced. As the stress ratio increases, the shear dilation gradually becomes the dominant mechanism, and the heat extraction performance is improved. The obtained results provide a practical guide for geothermal site siting and optimizing heat extraction efficiency in geothermal reservoirs.
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| 7. |
- Jing, Yumei, et al.
(författare)
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A Single-Electron Transistor Made of a 3D Topological Insulator Nanoplate
- 2019
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 31:42
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Tidskriftsartikel (refereegranskat)abstract
- Quantum confined devices of 3D topological insulators are proposed to be promising and of great importance for studies of confined topological states and for applications in low-energy-dissipative spintronics and quantum information processing. The absence of energy gap on the topological insulator surface limits the experimental realization of a quantum confined system in 3D topological insulators. Here, the successful realization of single-electron transistor devices in Bi2Te3 nanoplates using state-of-the-art nanofabrication techniques is reported. Each device consists of a confined central island, two narrow constrictions that connect the central island to the source and drain, and surrounding gates. Low-temperature transport measurements demonstrate that the two narrow constrictions function as tunneling junctions and the device shows well-defined Coulomb current oscillations and Coulomb-diamond-shaped charge-stability diagrams. This work provides a controllable and reproducible way to form quantum confined systems in 3D topological insulators, which should greatly stimulate research toward confined topological states, low-energy-dissipative devices, and quantum information processing.
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| 8. |
- Lin, Xiongwei, et al.
(författare)
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Noise reduction optimization of sound sensor based on a Conditional Generation Adversarial Network
- 2021
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1873:1
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Konferensbidrag (refereegranskat)abstract
- To address the problems in the traditional speech signal noise elimination methods, such as the residual noise, poor real-time performance and narrow applications a new method is proposed to eliminate network voice noise based on deep learning of conditional generation adversarial network. In terms of the perceptual evaluation of speech quality (PESQ) and shorttime objective intelligibility measure (STOI) functions used as the loss function in the neural network, which were used as the loss function in the neural network, the flexibility of the whole network was optimized, and the training process of the model simplified. The experimental results indicate that, under the noisy environment, especially in a restaurant, the proposed noise reduction scheme improves the STOI score by 26.23% and PESQ score by 17.18%, respectively, compared with the traditional Wiener noise reduction algorithm. Therefore, the sound sensor's noise reduction scheme through our approach has achieved a remarkable noise reduction effect, more useful information transmission, and stronger practicability.
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| 9. |
- Ng, Theam Foo, et al.
(författare)
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Justification of Fuzzy Declustering Vector Quantization Modeling in Classification of Genotype-Image Phenotypes
- 2010
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Konferensbidrag (refereegranskat)abstract
- With the fast development of multi‐dimensional data compression and pattern classification techniques, vector quantization (VQ) has become a system that allows large reduction of data storage and computational effort. One of the most recent VQ techniques that handle the poor estimation of vector centroids due to biased data from undersampling is to use fuzzy declustering‐based vector quantization (FDVQ) technique. Therefore, in this paper, we are motivated to propose a justification of FDVQ based hidden Markov model (HMM) for investigating its effectiveness and efficiency in classification of genotype‐image phenotypes. The performance evaluation and comparison of the recognition accuracy between a proposed FDVQ based HMM (FDVQ‐HMM) and a well‐known LBG (Linde, Buzo, Gray) vector quantization based HMM (LBG‐HMM) will be carried out. The experimental results show that the performances of both FDVQ‐HMM and LBG‐HMM are almost similar. Finally, we have justified the competitiveness of FDVQ‐HMM in classification of cellular phenotype image database by using hypotheses t‐test. As a result, we have validated that the FDVQ algorithm is a robust and an efficient classification technique in the application of RNAi genome‐wide screening image data.
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| 10. |
- Pham, Tuan D, et al.
(författare)
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A novel image feature for nuclear-phase classification in high content screening
- 2007
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Ingår i: Advances in Mass Data Analysis of Signals and Images in Medicine, Biotechnology and Chemistry. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540762997 - 9783540763000 ; , s. 84-93
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Bokkapitel (refereegranskat)abstract
- Cellular imaging is an exciting area of research in computational life sciences, which provides an essential tool for the study of diseases at the cellular level. In particular, to faciliate the usefulness of cellular imaging for high content screening, image analysis and classification need to be automated. In fact the task of image classification is an important component for any computerized imaging system which aims to automate the screening of high-content, high-throughput fluorescent images of mitotic cells. It can help biomedical and biological researchers to speed up the analysis of mitotic data at dynamic ranges for various applications including the study of the complexity of cell processes, and the screening of novel anti-mitotic drugs as potential cancer therapeutic agents. We propose in this paper a novel image feature based on a spatial linear predictive model. This type of image feature can be effectively used for vector-quantization based classification of nuclear phases. We used a dataset of HeLa cells line to evaluate and compare the proposed method on the classification of nuclear phases. Experimental results obtained from the new feature are found to be superior to some recently published results using the same dataset.
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