| 1. |
- Li, Yaokai, et al.
(författare)
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Mechanism study on organic ternary photovoltaics with 18.3% certified efficiency: from molecule to device
- 2022
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Ingår i: Energy & Environmental Science. - : ROYAL SOC CHEMISTRY. - 1754-5692 .- 1754-5706. ; 15:2, s. 855-865
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Tidskriftsartikel (refereegranskat)abstract
- Multi-component organic photovoltaics (OPVs), e.g., ternary blends, are effective for high performance, while the fundamental understanding from the molecular to device level is lacking. To address this issue, we here systematically study the working mechanism of ternary OPVs based on non-fullerene acceptors (NFAs). With both molecular dynamics simulations and morphology characterization, we identify that when adding another larger band gap and highly miscible NFA, namely IT-4F or BTP-S2, into the PBDB-TF:BTP-eC9 blend, the NFAs undergo molecular intermixing selectively with BTP-eC9. This causes the composition-dependent band gap and charge recombination, and hence the composition-dependent V-OC. While the charge recombination still dominantly occurs at the PBDB-TF:BTP-eC9 interface, BTP-S2 or IT-4F plays an auxiliary role in facilitating charge transfer and suppressing non-radiative decay. Interestingly, intermolecular end-group packing in the intermixed blend is improved compared to that in pristine films, leading to higher carrier mobility. These synergistic effects significantly improve the power conversion efficiency of the device to an outstanding value of 18.7% (certified value of 18.3%).
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| 2. |
- Li, Wen, et al.
(författare)
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Li+ ion conductivity and diffusion mechanism in α-Li3N and β-Li3N
- 2010
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Ingår i: Energy & environmental science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 3:10, s. 1524-1530
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Tidskriftsartikel (refereegranskat)abstract
- beta-Li3N of hexagonal D-6h(4) (P6(3)/mmc) structure was synthesized by high-energy ball milling commercial Li3N (composed of both alpha and beta phases). Ionic conductivities of alpha-Li3N and beta-Li3N were tested by direct current (D. C.) and alternating current (A. C.) impedance methods. beta-Li3N exhibited the same order of magnitude of Li+ ion conductivity (2.085 x 10(-4) S cm(-1)) as that of alpha-Li3N (5.767 x 10(-4) S cm(-1)) at room temperature. First-principles calculations were employed to simulate the diffusion mechanism of Li+ ion in alpha-Li3N and beta-Li3N. Our results indicate that the diffusion of Li+ ion in beta-Li3N likely occurs between pure Li-beta(1) planes, which is different from that in alpha-Li3N, where the diffusion of Li+ ion occurs within Li2N plane. The Li+ ion migration energy barriers (E-m) for alpha-Li3N and beta-Li3N are 0.007 eV and 0.038 eV, respectively.
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| 3. |
- Li, Wen, et al.
(författare)
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Li-Na ternary amidoborane for hydrogen storage : experimental and first-principles study
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:16, s. 4754-4764
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Tidskriftsartikel (refereegranskat)abstract
- Li-Na ternary amidoborane, Na[Li(NH2BH3)(2)], was recently synthesized by reacting LiH and NaH with NH3BH3. This mixed-cation amidoborane shows improved dehydrogenation performance compared to that of single-cation amidoboranes, i.e., LiNH2BH3 and NaNH2BH3. In this paper, we synthesized the Li-Na ternary amidoborane by blending and re-crystallizing equivalent LiNH2BH3 and NaNH2BH3 in tetrahydrofuran (THF), and employed first-principles calculations and the special quasirandom structure (SQS) method to theoretically explore the likelihood for the existence of Li1-xNax(NH2BH3) for various Li/Na ratios. The thermodynamic, electronic and phononic properties were investigated to understand the possible dehydrogenation mechanisms of Na[Li(NH2BH3)(2)].
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| 4. |
- Olson, Nathan D., et al.
(författare)
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precisionFDA Truth Challenge V2: Calling variants from short- and long-reads in difficult-to-map regions
- 2020
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The precisionFDA Truth Challenge V2 aimed to assess the state-of-the-art of variant calling in difficult-to-map regions and the Major Histocompatibility Complex (MHC). Starting with FASTQ files, 20 challenge participants applied their variant calling pipelines and submitted 64 variant callsets for one or more sequencing technologies (~35X Illumina, ~35X PacBio HiFi, and ~50X Oxford Nanopore Technologies). Submissions were evaluated following best practices for benchmarking small variants with the new GIAB benchmark sets and genome stratifications. Challenge submissions included a number of innovative methods for all three technologies, with graph-based and machine-learning methods scoring best for short-read and long-read datasets, respectively. New methods out-performed the 2016 Truth Challenge winners, and new machine-learning approaches combining multiple sequencing technologies performed particularly well. Recent developments in sequencing and variant calling have enabled benchmarking variants in challenging genomic regions, paving the way for the identification of previously unknown clinically relevant variants.
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| 5. |
- Olson, Nathan D., et al.
(författare)
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PrecisionFDA Truth Challenge V2: Calling variants from short and long reads in difficult-to-map regions
- 2022
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Ingår i: Cell Genomics. - : Elsevier BV. - 2666-979X. ; 2:5, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- The precisionFDA Truth Challenge V2 aimed to assess the state of the art of variant calling in challenging genomic regions. Starting with FASTQs, 20 challenge participants applied their variant-calling pipelines and submitted 64 variant call sets for one or more sequencing technologies (Illumina, PacBio HiFi, and Oxford Nanopore Technologies). Submissions were evaluated following best practices for benchmarking small variants with updated Genome in a Bottle benchmark sets and genome stratifications. Challenge submissions included numerous innovative methods, with graph-based and machine learning methods scoring best for short-read and long-read datasets, respectively. With machine learning approaches, combining multiple sequencing technologies performed particularly well. Recent developments in sequencing and variant calling have enabled benchmarking variants in challenging genomic regions, paving the way for the identification of previously unknown clinically relevant variants.
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| 6. |
- Qin, Linqing, et al.
(författare)
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Triplet Acceptors with a D-A Structure and Twisted Conformation for Efficient Organic Solar Cells
- 2020
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 59:35, s. 15043-15049
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Tidskriftsartikel (refereegranskat)abstract
- Triplet acceptors have been developed to construct high-performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T-1) are close to those of charge-transfer states ((CT)-C-3). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large pi-conjugated core and D-A structure, were confirmed to be triplet materials, leading to high-performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin-orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T-1 is close to (CT)-C-3, facilitating the split of triplet exciton to free charges.
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| 7. |
- Yang, Lei, et al.
(författare)
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Sulfur vs. tellurium: the heteroatom effects on the nonfullerene acceptors
- 2019
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Ingår i: Science in China Series B. - : SCIENCE PRESS. - 1674-7291 .- 1869-1870. ; 62:7, s. 897-903
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Tidskriftsartikel (refereegranskat)abstract
- The effect of chalcogen heteroatom variation on donor materials has been systematically investigated. However, this effect on acceptors has rarely been explored. Herein, nonfullerene acceptors BFPSP and BFPTP were reported by simply changing the chalcogen atoms from S to Te. The differences between BFPSP and BFPTP in light absorption, energy levels, excited-state lifetimes, energy loss, charge mobilities, morphology, and photovoltaic properties were systematically investigated to understand the heteroatom effects. More importantly, the electroluminescence spectra, external quantum efficiency of photovoltaics and TD-DFT calculations revealed that the triplet excited state (T-1) in energy of BFPTP equals to the charge transfer (CT) state in PBDB-T:BFPTP, which allows T-1 excitons, generated by intersystem crossing, to split into free charges to contribute to the efficiency. This contribution provides a strategy for tuning the photophysical properties of nonfullerene acceptors and designing high performance triplet materials for OSCs.
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| 8. |
- Yuan, Shuai, et al.
(författare)
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[Ti8Zr2O12(COO)(16)] Cluster : An Ideal Inorganic Building Unit for Photoactive Metal-Organic Frameworks
- 2018
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Ingår i: Acs Central Science. - : American Chemical Society (ACS). - 2374-7943 .- 2374-7951. ; 4:1, s. 105-111
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Tidskriftsartikel (refereegranskat)abstract
- Metal-organic frameworks (MOFs) based on Ti-oxo clusters (Ti-MOFs) represent a naturally self-assembled superlattice of TiO2 nanoparticles separated by designable organic linkers as antenna chromophores, epitomizing a promising platform for solar energy conversion. However, despite the vast, diverse, and well-developed Ti-cluster chemistry, only a scarce number of Ti-MOFs have been documented. The synthetic conditions of most Ti-based clusters are incompatible with those required for MOF crystallization, which has severely limited the development of Ti-MOFs. This challenge has been met herein by the discovery of the [Ti8Zr2O12(COO)(16)] cluster as a nearly ideal building unit for photoactive MOFs. A family of isoreticular photoactive MOFs were assembled, and their orbital alignments were fine-tuned by rational functionalization of organic linkers under computational guidance. These MOFs demonstrate high porosity, excellent chemical stability, tunable photoresponse, and good activity toward photocatalytic hydrogen evolution reactions. The discovery of the [Ti8Zr2O12(COO)(16)] cluster and the facile construction of photoactive MOFs from this cluster shall pave the way for the development of future Ti-MOF-based photocatalysts. GRAPHICS
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