| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Cao, Jian, et al.
(författare)
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Heterogeneous consecutive reaction kinetics of direct oxidation of H2 to H2O2: Effect and regulation of confined mass transfer
- 2023
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Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 455
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Tidskriftsartikel (refereegranskat)abstract
- Porous catalysts in heterogeneous reactions have played an important role in the modern chemical industry, but it is still challenging to quantitatively describe mass transfer and surface reaction behaviors of reactants in nano-confined space. Direct synthesis of hydrogen peroxide (H2O2) is considered as an attractive alternative to anthraquinone oxidation process, while the confined mass transfer of H2O2 in porous catalysts limits the reactivity. In this work, taking the consecutive reaction of H2O2 synthesis as an example, a quantitative method in modeling the effects of confined mass transfer on the reactivity was studied. More specifically, calorimetry was developed to characterize the confined structures of porous carbon experimentally, the linear nonequilibrium thermodynamics and the statistical mechanics method were further combined. Then, the heterogeneous consecutive reaction kinetics and the Thiele modulus influenced by confined mass transfer were modeled. Consequently, regulation strategies were proposed with the help of theoretical models. The optimized catalyst with biological skeleton carbon support and 0.5 wt% palladium loading shows an excellent catalytic performance. Lastly, for the mesoscience in heterogeneous reaction, the resistance was explored as a quantitative descriptor to compromise in the competition between mass transfer and surface reaction. The mesoscale structures were considered as the dynamic spatiotemporal distribution of substance concentrations, and the resistance minimization multi-scale (RMMS) model was proposed.
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| 3. |
- Du, Siying, et al.
(författare)
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Nonfullerene acceptors from thieno[3,2-b]thiophene-fused naphthalene donor core with six-member-ring connection for efficient organic solar cells
- 2021
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Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 185
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive design ideas on the fused-ring donor-core in state-of-the-art acceptor-donor-acceptor (A-D-A) nonfullerene acceptors (NFAs) are still of great importance for regulating the electron push-pull effect for the sake of optimal light-harvesting, frontier molecular orbital levels, and finally their photovoltaic properties. Herein, thieno[3,2-b]thiophenes were fused in bay-area of naphthalene via six-member-ring connection, resulting in the formation of dihydropyrenobisthieno[3,2-b]thiophene based octacyclic ladder-type donor core, which was flanked by two 1,1-dicyanomethylene-3-indanone (IC) acceptor motifs with and without 5,6-diflourination, namely PTT-IC and PTT-2FIC, respectively, as novel efficient A-D-A fused-ring electron acceptors (FREAs). Compared with PTT-IC, fluorinated PTT-2FIC possesses narrower optical bandgap of 1.48 eV, better π-π stacking, and its PBDB-T:PTT-2FIC blend film exhibited better morphology, and better hole and electron mobility. As a result, nonfullerene solar cells using PBDB-T:PTT-2FIC as the active layer achieved a decent PCE of 10.40%, with an open-circuit voltage (VOC) of 0.87 V, a fill factor (FF) of 0.65, and a much higher short-circuit current (JSC) of 18.26 mA/cm2. Meanwhile, the PBDB-T:PTT-IC cells delivered a lower JSC of 12.58 mA/cm2 but a higher VOC of 0.99 V, thus resulting in a PCE of 7.39% due to its wider optical bandgap of 1.58 eV and higher LUMO energy level. These results demonstrated that NFAs based on fused-ring donor core from fusing thieno[3,2-b]thiophenes with naphthalene via six-member-ring connection are promising for organic photovoltaic applications.
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| 4. |
- Li, Cheng, et al.
(författare)
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A diketopyrrolopyrrole-based macrocyclic conjugated molecule for organic electronics
- 2019
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 7:13, s. 3802-3810
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the first diketopyrrolopyrrole (DPP) based donor-acceptor macrocyclic conjugated molecule was developed and its application in organic electronics was systematically studied. Macrocyclic molecules, as a fragment of armchair carbon nanotubes, have emerged as functional materials in materials chemistry, but the materials are always limited to cycloparaphenylenes. Using the donor-acceptor design strategy that has been widely used in high performance conjugated polymers for macrocyclic molecules, it will significantly broaden their species with tunable optical and electrical properties. Herein, we synthesize a well-defined macrocyclic molecule containing four electron-deficient DPP units alternating with electron-rich thiophenes. The new molecule was found to show high solubility, near-infrared absorption spectra and 3D charge transport properties. The new macrocyclic molecule as an electron acceptor was applied to non-fullerene organic solar cells, exhibiting an initial efficiency of 0.49%, while the linear molecule with a similar backbone only showed a very low efficiency of 0.03%. Our results demonstrate that donor-acceptor macrocyclic conjugated materials have great potential application in organic electronics.
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| 5. |
- Li, Shuixing, et al.
(författare)
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Unveiling structure-performance relationships from multi-scales in non-fullerene organic photovoltaics
- 2021
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Unveiling the correlations among molecular structures, morphological characteristics, macroscopic properties and device performances is crucial for developing better photovoltaic materials and achieving higher efficiencies. To achieve this goal, a comprehensive study is performed based on four state-of-the-art non-fullerene acceptors (NFAs), which allows to systematically examine the above-mentioned correlations from different scales. Its found that extending conjugation of NFA shows positive effects on charge separation promotion and non-radiative loss reduction, while asymmetric terminals can maximize benefits from both terminals. Another molecular optimization is from alkyl chain tuning. The shortened alkyl side chain results in strengthened terminal packing and decreased pi-pi distance, which contribute high carrier mobility and finally the high charge collection efficiency. With the most-acquired benefits from molecular structure and macroscopic factors, PM6:BTP-S9-based organic photovoltaics (OPVs) exhibit the optimal efficiency of 17.56% (certified: 17.4%) with a high fill factor of 78.44%, representing the best among asymmetric acceptor based OPVs. This work provides insight into the structure-performance relationships, and paves the way toward high-performance OPVs via molecular design. Understanding correlations between molecular structures and macroscopic properties is critical in realising highly efficient organic photovoltaics. Here, the authors conduct a comprehensive study based on four non-fullerene acceptors revealing how the extended conjugation, asymmetric terminals and alkyl chain length can affect device performance.
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| 6. |
- Li, Xiaofang, et al.
(författare)
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Roles of Acceptor Guests in Tuning the Organic Solar Cell Property Based on an Efficient Binary Material System with a Nearly Zero Hole-Transfer Driving Force
- 2020
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Ingår i: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 32:12, s. 5182-5191
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Tidskriftsartikel (refereegranskat)abstract
- Sub-picosecond hole transfer has been recently observed in several narrow band gap nonfullerene small-molecule acceptor (NFA)-based binary blended organic solar cell (OSC) systems operating with negligible energetic driving forces. As the driving forces are near zero, how the added acceptor/donor guests tune the barrier-free hole-transfer dynamics of these systems remains very unclear. In this study, we report a new NFA (BTCT-2Cl) that conducts a sub-picosecond hole transfer (2 ps) for efficient photocurrent generation when pairing with PM6 though the energetic offset is only 0.02 eV. We observe that the added nonfullerene and PCBM components differently tune the charge generation and recombination when selectively exciting BTCT-2Cl. After adding PC71BM, the hole transfer from the host BTCT-2Cl to the host donor is greatly accelerated, with the rate significantly reduced to 0.29 ps and the charge generation becomes more efficient; on the contrary, recombination is prolonged and a larger fill factor is obtained after adding an NFA guest, here, IT-4F. The different tuning on the host binary hole-transfer dynamics is likely related with the phase crystallinity and the domain size changed after adding different acceptor guests. Over 16% efficiency is obtained on the PC71BM-based ternary device that outperforms the host binary and the IT-4F-based ternary solar cells (both showing over 15% efficiencies). The results clearly demonstrate that adding PCBM or NFA guests enables a very effective and different tuning on the hole-transfer rates and the recombination rates between the barrier-free host binary components, hence leading to efficient tuning on the short-circuit current density and fill factor, which outlines new strategies toward designing high-efficiency ternary blended OSC systems.
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| 7. |
- 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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| 8. |
- Wang, Jianqiu, et al.
(författare)
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A Comparative Study on Hole Transfer Inversely Correlated with Driving Force in Two Non-Fullerene Organic Solar Cells
- 2019
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 10:14, s. 4110-4116
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Tidskriftsartikel (refereegranskat)abstract
- We report a faster rate of hole transfer under a smaller AHomo in a comparative study of two group organic solar cells (OSCs) consisting of IT-4F as an acceptor and PBDBT and PBDBT-SF as donors. In the OSCs based on PBDBT. SF:IT-4F, a higher short-circuit current (J(SC)) was observed with a Delta(Homo) of 0.31 eV compared to a lower Jsc in PBDBT:IT-4F OSCs with a larger Delta(Homo) (0.45 eV). Intensive investigation indicates that the rate of transfer of a hole from IT-4F to PBDBT-SF or PBDBT is inversely proportional to the Delta(Homo) between IT-4F and donors. The larger Jsc in the PBDBT-SF:IT-4F device is attributed to a synergy of faster hole transfer, slower recombination, and rapid charge extraction enabled by desired morphology and balanced charge carrier mobilities with PBDBT-SF, suggesting that under a sufficiently high Delta(Homo), comprehensive considerations of the transport, film morphology, and energy levels are needed when designing new materials for high-performance OSCs.
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| 9. |
- Wang, Jianqiu, et al.
(författare)
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Fast Field-Insensitive Charge Extraction Enables High Fill Factors in Polymer Solar Cells
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:34, s. 38460-38469
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Tidskriftsartikel (refereegranskat)abstract
- Fill factor (FF) is a determining parameter for the power conversion efficiency (PCE) of organic solar cells (OSC). So far, nonfullerene (NF) OSCs with state-of-the-art PCEs exhibit FFs <0.8, lower than the values of Si or perovskite solar cells. The FFs directly display the dependence of photocurrent on bias, meaning that the competition between charge extraction and recombination is modulated by internal electric potential (V-in). Here, we report a study to understand key parameters/properties affecting the device FF based on seven groups of NF-OSCs consisting of widely used PBDBT-2F or PTB7-Th donors and representative NF-acceptors with FFs ranging from 0.60 to 0.78 and PCEs from 10.27 to 16.09%. We used field-dependent transient photocurrent measurements to reveal that fast and field-insensitive charge extraction at low V-in is an essential prerequisite for obtaining high FFs (0.75-0.8), which is enabled by balanced charge transport in steady and reduced bimolecular charge recombination in high purity phases. With bias-dependent quantum efficiency analysis, we further show that the recombination loss at low V-in in the devices with low FFs tends to be more significant involving excitons generated in the donor phase of blends. Our results provide relevance for how to improve the FF toward the boost of photovoltaic performance in NF-OSCs.
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| 10. |
- Xia, Xinxin, et al.
(författare)
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Revealing the crystalline packing structure of Y6 in the active layer of organic solar cells: the critical role of solvent additives
- 2023
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 11:40, s. 21895-21907
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Tidskriftsartikel (refereegranskat)abstract
- The bulk heterojunction (BHJ) morphology of photovoltaic materials is crucial to the fundamental optoelectronic properties of organic solar cells (OSCs). However, in the photoactive layer, the intrinsic crystalline packing structure of Y6, currently the hallmark molecule among Y-series non-fullerene acceptors (NFAs), has not been unambiguously determined. Here, employing grazing-incidence wide-angle X-ray scattering (GIWAXS), we managed to uncover the intrinsic crystalline packing structure of Y6 in the BHJ active layer of OSCs, which is found to be different from its single-crystal structure reported previously. Moreover, we find that solvent additive 1-chloronaphthalene (CN) can induce highly ordered packing of Y6 in BHJ thin films. With the help of atomistic molecular dynamics simulations, it is revealed that pi-pi interactions generally exist between naphthalene derivatives and IC terminals of Y6 analogues, which would essentially improve their long-range ordering. Our work reveals the intrinsic crystalline packing structure of Y6 in the BHJ active layer as well as its crystallization mechanism in thin films, thus providing direct correlations between this crystalline packing and the device characteristics and photophysical properties.
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