| 1. |
- He, Chengliang, et al.
(författare)
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Asymmetric electron acceptor enables highly luminescent organic solar cells with certified efficiency over 18%
- 2022
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Enhancing the luminescence property without sacrificing the charge collection is one key to high-performance organic solar cells (OSCs), while limited by the severe non-radiative charge recombination. Here, we demonstrate efficient OSCs with high luminescence via the design and synthesis of an asymmetric non-fullerene acceptor, BO-5Cl. Blending BO-5Cl with the PM6 donor leads to a record-high electroluminescence external quantum efficiency of 0.1%, which results in a low non-radiative voltage loss of 0.178 eV and a power conversion efficiency (PCE) over 15%. Importantly, incorporating BO-5Cl as the third component into a widely-studied donor:acceptor (D:A) blend, PM6:BO-4Cl, allows device displaying a high certified PCE of 18.2%. Our joint experimental and theoretical studies unveil that more diverse D:A interfacial conformations formed by asymmetric acceptor induce optimized blend interfacial energetics, which contributes to the improved device performance via balancing charge generation and recombination. High-performance organic solar cells call for novel designs of acceptor molecules. Here, He et al. design and synthesize a non-fullerene acceptor with an asymmetric structure for diverse donor:acceptor interfacial conformations and report a certificated power conversion efficiency of 18.2%.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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