| 1. |
- Wu, Jingnan, 1994, et al.
(author)
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Modulating the nanoscale morphology on carboxylate-pyrazine containing terpolymer toward 17.8% efficiency organic solar cells with enhanced thermal stability
- 2022
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 446
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Journal article (peer-reviewed)abstract
- It had been commonly accepted in the organic photovoltaic (OPV) community that subtle variations in the molecular structure of active layer materials would cause profound impacts on their aggregating structure and blend morphology and therefore the performance of such polymer solar cells (PSCs). Herein, we employed an electron-deficient building block 3,6-dithiophenyl-2-carboxylate pyrazine (DTCPz) for constructing one series of promising donor terpolymers of PMZ1, PMZ2, and PMZ3, respectively, gaining their relatively lower-lying highest occupied molecular orbital (HOMO) energy levels, more closed π-π stacking and enhanced crystallinity in thin films, and lower miscibility with acceptor Y6, in comparison with their parent polymer counterpart (namely PM6). Reaching DTCPz moieties up to 20% (mol/mol%) in its terpolymer composition, the resulting polymer (PMZ2) achieved more favorable phase separation with improved exciton dissociation, and charge transport and extraction. As a result, an outstanding fill factor of 77.2% and a promising power conversion efficiency of 17.8 % was achieved. Moreover, the corresponding device shows better thermal stability over the PM6-based one. This work suggests a facile method for significantly improving the thin film morphology of the active-layer materials via fine-tuning the chemical structure of electron-deficient units on the backbone of the wide bandgap donor polymer, therefore achieving enhanced photovoltaic performance and thermal stability for practical applications.
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| 2. |
- Fan, Baobing, et al.
(author)
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Correlation of Local Isomerization Induced Lateral and Terminal Torsions with Performance and Stability of Organic Photovoltaics
- 2023
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In: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 145:10, s. 5909-5919
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Journal article (peer-reviewed)abstract
- Organic photovoltaics (OPVs) have achieved great progress in recent years due to delicately designed non-fullerene acceptors (NFAs). Compared with tailoring of the aromatic heterocycles on the NFA backbone, the incorporation of conjugated side-groups is a cost-effective way to improve the photoelectrical properties of NFAs. However, the modifications of side-groups also need to consider their effects on device stability since the molecular planarity changes induced by side-groups are related to the NFA aggregation and the evolution of the blend morphology under stresses. Herein, a new class of NFAs with localisomerized conjugated side-groups are developed and the impact of local isomerization on their geometries and device performance/stability are systematically investigated. The device based on one of the isomers with balanced side- and terminal-group torsion angles can deliver an impressive power conversion efficiency (PCE) of 18.5%, with a low energy loss (0.528 V) and an excellent photo- and thermal stability. A similar approach can also be applied to another polymer donor to achieve an even higher PCE of 18.8%, which is among the highest efficiencies obtained for binary OPVs. This work demonstrates the effectiveness of applying local isomerization to fine-tune the side-group steric effect and non-covalent interactions between side-group and backbone, therefore improving both photovoltaic performance and stability of fused ring NFA-based OPVs.
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| 3. |
- Li, Shuixing, et al.
(author)
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Unveiling structure-performance relationships from multi-scales in non-fullerene organic photovoltaics
- 2021
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)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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| 4. |
- Liao, Xunfan, et al.
(author)
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Regulating Favorable Morphology Evolution by a Simple Liquid-Crystalline Small Molecule Enables Organic Solar Cells with over 17% Efficiency and a Remarkable J(sc) of 26.56 mA/cm(2)
- 2021
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 33:1, s. 430-440
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Journal article (peer-reviewed)abstract
- Liquid crystal small molecules (LCSMs) are manifested as the effective additives to regulate the morphology of active layers and elevate the performance of ternary organic solar cells (TOSCs) in fullerene systems. However, the current studies for TOSCs based on efficient LCSMs are most out of the LC phase transition temperature, which is not conducive to accurately disclosure the effect of LCSMs on the morphology evolution. Besides, the inner working mechanism of LCSMs has not been investigated systematically and in-depth. Herein, a structurally simple donor-acceptor-donor type LCSM DFBT-TT6 with a low liquid crystal phase transition temperature is utilized as the third component to construct TOSCs based on a highly efficient nonfullerene system PM6:Y6. To unveil the work mechanism of LCSMs on the TOSCs performance and eliminate other interferences simultaneously, a structurally similar non-LCSM DFBT-DT6 with a low glass-transition temperature is further synthesized for a more clear comparison. Interestingly, the addition of DFBT-TT6 can delicately control the crystallinity and phase separation of PM6:Y6, rendering the optimized morphology with only 3 wt % DFBT-TT6. In contrast, the non-LCSM DFBT-DT6 shows a negligible effect on morphology regulation, indicating the unique ability of LC molecules in morphology control. The underlying working mechanism is revealed by the combined study of miscibility and the wetting coefficient of the blends, elucidating that the LCSM DFBT-TT6 has good compatibility with PM6 and Y6. Therefore, DFBT-TT6 is more prone to being located at the interface of PM6 and Y6, and it is energetically favorable for charge transfer. The aforementioned favorable morphology evolution is associated with improved crystallinity, phase separation, charge transfer, exciton dissociation, and collection efficiency, ultimately boosting the power conversion efficiency of TOSCs from 15.76% to 17.05% with a remarkable short-circuit current density of 26.56 mA/cm(2). This work not only offers deep insight into the LCSM induced morphology evolution but also puts forward an affordable strategy to achieve high-performance TOSCs.
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| 5. |
- Wen, Tian-Jiao, et al.
(author)
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Non-fused medium bandgap electron acceptors for efficient organic photovoltaics
- 2022
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In: Journal of Energy Challenges and Mechanics. - : ELSEVIER. - 2056-9386. ; 70, s. 576-582
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Journal article (peer-reviewed)abstract
- The cost-effective organic semiconductors are strongly needed in organic photovoltaics (OPVs). Herein, two medium bandgap (MBG) electron acceptors, TPT4F and TPT4Cl are developed via the new design of multi-noncovalent interaction assisted unfused core, flanked with two electron withdrawing end groups. These fullly non-fused MBG acceptors adapt the planar and rigid conformation in solid, therefore exhibiting the ordered face-on stacking and strong photoluminescence in films. As results, TPT4Cl-based OPVs, upon blending with the PBDB-TF polymer donor, have achieved a power conversion efficiency of 10.16% with a low non-radiative loss of 0.27 eV, representing one of the best fullly non-fused medium bandgap acceptors with desirable cost-efficiency balance. (c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.
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| 6. |
- Xia, Changjiu, et al.
(author)
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Regeneration of Deactivated Hollow Titanium Silicalite Zeolite from Commercial Ammoximation Process by Encapsulating Amorphous TiO2-SiO2 Nanoparticles inside Zeolite Crystal
- 2016
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In: ChemistrySelect. - : Wiley. - 2365-6549. ; 1:14, s. 4187-4192
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Journal article (peer-reviewed)abstract
- An efficient regeneration method to encapsulate the poisonous amorphous TiO2-SiO2 nanoparticles within zeolite crystal via post-synthesis has been developed. It is demonstrated that the encapsulation of Ti-rich nanoparticles can reduce the accessibility of H2O2 molecules to acid sites of Ti-rich nanoparticles, thus lowering the inefficient decomposition of H2O2 oxidant during catalytic reactions. Furthermore, the regenerated HTS zeolite is of smaller particle size than conventional TS-1 zeolite due to the existence of deactivated HTS as crystal seed during hydrothermal synthesis. Consequently, the regenerated HTS zeolite shows as high catalytic performance as fresh TS-1 zeolite in phenol hydroxylation reaction with 30 wt% H2O2 aqueous solution as oxidant. Importantly, this study exploits a novel concept on updating the lifetime of industrial zeolite catalyst, which is of both academic and practical significance.
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| 7. |
- Xia, Xinxin, et al.
(author)
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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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In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 11:40, s. 21895-21907
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Journal article (peer-reviewed)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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| 8. |
- Xia, Yangyang, et al.
(author)
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Prediction of bending strength of glass fiber reinforced methacrylate-based pipeline UV-CIPP rehabilitation materials based on machine learning
- 2023
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In: Tunnelling and Underground Space Technology. - : Elsevier. - 0886-7798 .- 1878-4364. ; 140
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Journal article (peer-reviewed)abstract
- Ultraviolet cured-in-place-pipe (UV-CIPP) materials are commonly used in trenchless pipeline rehabilitation. Their bending strength is a crucial indicator to evaluate the curing quality. Studies show that this indicator is affected by multiple factors, including the curing time, UV lamp curing power, curing distance, and material thickness. Laboratory experiments have limitations in analyzing the effect of multiple factors on the bending strength of UV-CIPP materials and quantitatively predicting the optimum curing parameters. Aiming at resolving these shortcomings, resolve machine learning techniques were applied to predict the bending strength. In this regard, the surface curing reaction temperature monitoring data and three-point bending data of 30 groups of UV-CIPP material under the influence of different curing parameters were used as a dataset to predict the bending strength of UV-CIPP material. The results show that the influence degree of each factor on the bending strength of the UV-CIPP material, from high to low, is as follows: UV lamp power (−0.439), the temperature at the illuminated side (−0.392), curing time (−0.323), the temperature at the back side (−0.233), curing distance (0.143) and material thickness (−0.140). The best penalty parameter c (44.435) and width g (0.072) of the kernel function in the support vector machine (SVM) model were obtained using the genetic algorithm (GA) optimization, and the results were compared with the grey wolf optimizer (GWO) and particle swarm optimization (PSO). The performed analyses revealed that the developed GA-SVM model exhibits the best prediction results compared to other machine learning algorithms. The optimum bending strength of the UV-CIPP material used in this test is 294.77 MPa, which corresponds to the curing time, UV lamp power, curing distance, material thickness, light side temperature, and back side temperature of 7.59 min, 157.33 mW/cm2, 189.99 mm, 4.38 mm, 79.49 °C, and 76.59 °C, respectively.
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