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| 2. |
- Yuan, Jun, et al.
(author)
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Enabling low voltage losses and high photocurrent in fullerene-free organic photovoltaics
- 2019
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In: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
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Journal article (peer-reviewed)abstract
- Despite significant development recently, improving the power conversion efficiency of organic photovoltaics (OPVs) is still an ongoing challenge to overcome. One of the prerequisites to achieving this goal is to enable efficient charge separation and small voltage losses at the same time. In this work, a facile synthetic strategy is reported, where optoelectronic properties are delicately tuned by the introduction of electron-deficient-core-based fused structure into non-fullerene acceptors. Both devices exhibited a low voltage loss of 0.57 V and high short-circuit current density of 22.0 mA cm(-2), resulting in high power conversion efficiencies of over 13.4%. These unconventional electron-deficient-core-based non-fullerene acceptors with near-infrared absorption lead to low non-radiative recombination losses in the resulting organic photovoltaics, contributing to a certified high power conversion efficiency of 12.6%.
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| 3. |
- Ma, Qing, et al.
(author)
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Promoting charge separation resulting in ternary organic solar cells efficiency over 17.5%
- 2020
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In: Nano Energy. - : ELSEVIER. - 2211-2855 .- 2211-3282. ; 78
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Journal article (peer-reviewed)abstract
- Ternary blend has been an effective strategy for achieving high efficiency in organic solar cells (OSCs). Herein, a non-fullerene small molecule acceptor (C8-DTC) was synthesized and added to the PM6: Y6 system as a third component. By adding 10% of C8-DTC as the second acceptor in the PM6:Y6 system, an impressive power conversion efficiency of 17.52% was achieved with simultaneously increased open-circuit voltage, short-circuit current-density, and fill factor. The reduced voltage loss was due to the lowered non-radiative recombination loss in comparison with the binary device. It was also found that a small amount of C8-DTC in the PM6:Y6 blend resulted in enhanced charge separation and charge transport by providing possible extra channels of hole extraction. And the ternary system formed a good phase separation and favored bi-continuous transport network, which is more conducive to balance the electron and hole transport. The results indicate that the ternary system formed by C8-DTC as the third component is an effective method to improve the performance of the PM6:Y6 based OSCs.
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| 4. |
- Weng, Zebin, et al.
(author)
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Performance improvement of variable-angle annular thermoelectric generators considering different boundary conditions
- 2022
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 306
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Journal article (peer-reviewed)abstract
- Practical applications of thermoelectric generators are impeded by their low thermoelectric conversion efficiency, and improving the efficiency is vital for the advancements of thermoelectric technology. In this paper, a novel method is proposed for the performance analysis and improvement of the annular thermoelectric generators with variable-angle PN legs (VATEGs). The influence of the PN leg angle on the output performance of the VATEG is investigated by introducing an angle function. Given the volume of the PN legs, the relationship of output performance between the VATEG and traditional constant-angle ATEG (CATEG) is established under different boundary conditions based on a proposed generic model of VATEG. The results are verified numerically using the finite element method. Using the model, it is shown that the output performance of the VATEG is significantly affected by the shape of the PN leg. Finally, the thermal stress on the PN leg is next investigated using a high-fidelity 3D model of the variable-angle PN legs implemented in COMSOL, and it is found that the shape difference has a considerable influence on the thermal stability of VATEG. Under the condition of constant heat flux on the hot side and constant temperature on the cold side of the thermoelectric modules, it shows that when the radius factor is 2, the output performance can be improved by 35% with the designed VATEG, at the expense of 30% higher maximum thermal stress on the PN legs.
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| 5. |
- Xu, Lei, et al.
(author)
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The Role of Solution Aggregation Property toward High-Efficiency Non-Fullerene Organic Photovoltaic Cells
- 2024
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In: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095.
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Journal article (peer-reviewed)abstract
- In organic photovoltaic cells, the solution-aggregation effect (SAE) is long considered a critical factor in achieving high power-conversion efficiencies for polymer donor (PD)/non-fullerene acceptor (NFA) blend systems. However, the underlying mechanism has yet to be fully understood. Herein, based on an extensive study of blends consisting of the representative 2D-benzodithiophene-based PDs and acceptor-donor-acceptor-type NFAs, it is demonstrated that SAE shows a strong correlation with the aggregation kinetics during solidification, and the aggregation competition between PD and NFA determines the phase separation of blend film and thus the photovoltaic performance. PDs with strong SAEs enable earlier aggregation evolutions than NFAs, resulting in well-known polymer-templated fibrillar network structures and superior PCEs. With the weakening of PDs' aggregation effects, NFAs, showing stronger tendencies to aggregate, tend to form oversized domains, leading to significantly reduced external quantum efficiencies and fill factors. These trends reveal the importance of matching SAE between PD and NFA. The aggregation abilities of various materials are further evaluated and the aggregation ability/photovoltaic parameter diagrams of 64 PD/NFA combinations are provided. This work proposes a guiding criteria and facile approach to match efficient PD/NFA systems. A systematic study of the representative organic photovoltaic systems shows that the aggregation competition between polymer donor (PD) and non-fullerene acceptor (NFA) is a decisive factor in the phase separation of blend film and thus the photovoltaic performance. Based on 64 PD/NFA combinations, the aggregation ability/photovoltaic parameter heatmaps are plotted, providing a new matching rule for developing high-efficiency PD/NFA systems. image
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| 6. |
- Yang, Wenlong, et al.
(author)
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Performance improvement and thermomechanical analysis of a novel asymmetrical annular thermoelectric generator
- 2024
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In: Applied Thermal Engineering. - 1359-4311. ; 237
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Journal article (peer-reviewed)abstract
- Enhancing thermoelectric performance hinges on optimizing the geometry of thermoelectric legs. In this study, we present a novel asymmetrical annular thermoelectric generator (ATEG) in which the proportions of P-type and N-type legs are meticulously balanced. We construct a one-dimensional analytical model tailored to this ATEG. Utilizing this model, we derive the relationship governing thermal-electrical impedance matching in an asymmetrical ATEG and formulate a general expression for optimizing the asymmetry coefficient. We explore the influence of various thermal boundary conditions on optimal impedance matching, ideal annular leg parameters, and the optimal asymmetry coefficient. Our findings reveal that thermal boundary conditions significantly affect the optimal load ratio. Furthermore, in comparison to traditional ATEGs, our proposed asymmetrical ATEG with the optimized structure exhibits a remarkable 16.2 % increase in output power while maintaining the same material volume. Additionally, we perform a three-dimensional numerical analysis of the asymmetrical ATEG using Comsol. Our research findings indicate that introducing the asymmetric structure leads to higher maximum thermal stress on the legs. Interestingly, the study of asymmetric thermal boundary conditions highlights that improving heat transfer between the ATEG and the cooler yields higher mechanical reliability compared to enhancing heat transfer between the ATEG and the heat source.
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