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- Liao, Xunfan, et al.
(författare)
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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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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 33:1, s. 430-440
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Liao, Xunfan, et al.
(författare)
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The role of dipole moment in two fused-ring electron acceptor and one polymer donor based ternary organic solar cells
- 2020
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 4:5, s. 1507-1518
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Tidskriftsartikel (refereegranskat)abstract
- Fused-ring electron acceptor (FREA) based ternary organic solar cells (OSCs) have made significant progress and attracted considerable attention due to their simple device architecture and broad absorption range in devices. There are three key parameters that need to be fine-tuned in ternary OSCs including absorption, energy level and morphology in order to realize high efficiencies. Herein, a series of FREAs with diverse electron-rich cores or electron-deficient terminals are developed and rationally combined to achieve high performance ternary OSCs. The dipole moment of FREAs' terminals has been unveiled as an important factor and its working mechanism has been thoroughly investigated by systematically studying six ternary OSCs. These ternary blends all exhibit complementary absorption and cascade energy levels, which can facilitate efficient light-harvesting and charge transfer. Additionally, the morphological effects on ternary OSCs are eliminated through comparative studies while demonstrating distinctively different performance. The preliminary results show that compatible dipole moment between two FREAs is critical in ternary blends. Specifically, the performance of the ternary system with two FREAs having quite different dipole moment terminals is worse compared to that with similar terminal dipole moments. The pair with larger difference in the dipole moment will also negatively impact device performance. This interesting phenomenon is likely due to the fact that very different dipole moments of terminals in FREAs can significantly decrease the electron mobility as well as induce unbalanced hole/electron transport. Consequently, it results in increased charge recombination and reduced charge collection efficiency. This finding demonstrates that the dipole moment of FREAs should be taken into account in designing ternary OSCs.
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| 3. |
- Xu, Guodong, et al.
(författare)
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Reducing Energy Loss and Morphology Optimization Manipulated by Molecular Geometry Engineering for Hetero-junction Organic Solar Cells
- 2020
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Ingår i: Chinese journal of chemistry. - : WILEY-V C H VERLAG GMBH. - 1001-604X .- 1614-7065. ; 38:12, s. 1553-1559
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Tidskriftsartikel (refereegranskat)abstract
- A Summary of main observation and conclusion Molecular geometry engineering is an effective strategy to control the micromorphology and molecular energy level in organic photovoltaics (OPVs). Two novel copolymers based on alkylsilyl- and chloride-functionalized benzodithiophene (BDT) were designed and synthesized for wide bandgap copolymer donor materials in OPVs. It was found that the two copolymers exhibited distinctly different properties in active layer when blended with fullerene-free acceptor IT-4F. The chloride-functionalized copolymer PBDTCl-TZ with deeper molecular energy level and better coplanar structure induced more ordered aggregation in blend film. Thus, the device based on PBDTCl-TZ exhibits better energy alignment with IT-4F and smaller radiative recombination. Furthermore, the non-radiative recombination of PBDTCl-TZ:IT-4F based device is about 45 mV lower than the PBDTSi-TZ:IT-4F based device, contributing to a lower energy loss (E-loss), and a higher open-circut voltage (V-OC). As a result, the devices based on the blend of PBDTCl-TZ:IT-4F exhibit a high power conversion efficiency (PCE) of up to 12.2% with a highV(OC)of 0.837 V, higher than that of PBDTSi-TZ:IT-4F, of which the PCE is 11.2% with a V-OC of 0.781 V.
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| 4. |
- Yao, Zhaoyang, et al.
(författare)
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Exploring Overall Photoelectric Applications by Organic Materials Containing Symmetric Donor Isomers
- 2019
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Ingår i: Chemistry of Materials. - : American Concrete Institute. - 0897-4756 .- 1520-5002. ; 31:21, s. 8810-8819
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Tidskriftsartikel (refereegranskat)abstract
- Organic thin-film solar cells have demonstrated a bright prospect for commercial applications, where organic photosensitizers act as the most important kernel. In the global motif of sustainable development, unrelenting research efforts have been devoted to the exploration of organic material containing photosensitizers to achieve low-cost conversion of solar energy to clean electricity. In this work, two star-shaped donor cores, T1 and T2, which consist of fused thiophene triazatruxene, have been synthesized and applied in two different types of solar cells. The two-dimensional pi-bonded extension enhances their electron-donating capability and induces relatively strong intermolecular pi-pi stacking. The C-3h symmetrical donor isomers, featuring planar backbones and three-dimensional structures, are found to contribute toward a promising prospect for overall photoelectric applications.
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