| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Chai, Gaoda, et al.
(författare)
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Deciphering the Role of Chalcogen-Containing Heterocycles in Nonfullerene Acceptors for Organic Solar Cells
- 2020
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Ingår i: ACS Energy Letters. - : AMER CHEMICAL SOC. - 2380-8195. ; 5:11, s. 3415-3425
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Tidskriftsartikel (refereegranskat)abstract
- The field of organic solar cells has experienced paradigm-shifting changes in recent years because of the emergence of nonfullerene acceptors (NFAs). It is critically important to gain more insight into the structure-property relationship of the emerging A-DAD-A-type NFAs. In this Letter, a family of NFAs named BPF-4F, BPT-4F, and BPS-4F incorporating various chalcogen-containing heterocycles, i.e., furan, thiophene, and selenophene, respectively, was designed and synthesized. These NFAs exhibited dramatic differences in their photovoltaic performances with device efficiencies of 16.8% achieved by the thiophene-based cells, which was much higher than the furan-based ones (12.6%). In addition, the selenophene-based NFA showed a red-shifted absorption relative to the furan- and thiophene-based ones and obtained a decent efficiency of 16.3% owing to an improved J(SC). The reasons why these NFAs performed differently are systematically studied by comparing their optoelectronic properties and film morphology, which provides new understandings of the molecular design of high-performance NFAs.
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| 3. |
- Fan, Qunping, 1989, et al.
(författare)
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High-performance all-polymer solar cells enabled by a novel low bandgap non-fully conjugated polymer acceptor
- 2021
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Ingår i: Science in China Series B. - : Springer Nature. - 1674-7291 .- 1869-1870. ; 64, s. 1380-1388
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Tidskriftsartikel (refereegranskat)abstract
- Anon-fully conjugated polymer as a new class of acceptor materials has shown some advantages over its small molecular counterpart when used in photoactive layers for all-polymer solar cells (all-PSCs), despite a low power conversion efficiency (PCE) caused by its narrow absorption spectra. Herein, a novel non-fully conjugated polymer acceptor PFY-2TS with a low bandgap of similar to 1.40 eV was developed, via polymerizing a large pi-fused small molecule acceptor (SMA) building block (namely YBO) with a non-conjugated thioalkyl linkage. Compared with its precursor YBO, PFY-2TS retains a similar low bandgap but a higher LUMO level. Moreover, compared with the structural analog of YBO-based fully conjugated polymer acceptor PFY-DTC, PFY-2TS shows similar absorption spectrum and electron mobility, but significantly different molecular crystallinity and aggregation properties, which results in optimal blend morphology with a polymer donor PBDB-T and better device physical processes in all-PSCs. As a result, PFY-2TS-based all-PSCs achieved a PCE of 12.31% with a small energy loss of 0.56 eV enabled by the reduced non-radiative energy loss (0.24 eV), which is better than that of 11.08% for the PFY-DTC-based ones. Our work clearly demonstrated that non-fully conjugated polymers as a new class of acceptor materials are very promising for the development of high-performance all-PSCs.
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| 4. |
- Pan, Junxiu, et al.
(författare)
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pi-Extended Nonfullerene Acceptors for Efficient Organic Solar Cells with a High Open-Circuit Voltage of 0.94 V and a Low Energy Loss of 0.49 eV
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 13:19, s. 22531-22539
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Tidskriftsartikel (refereegranskat)abstract
- A combination of high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) typically creates effective organic solar cells (OSCs). Y5, a member of the Y-series acceptors, can achieve high V-oc of 0.94 V with PM6 but low J(sc) of 12.8 mA cm(-2). To maintain the high V-oc while increasing the J(sc) of devices, we developed a new nonfullerene acceptor, namely, BTP-C2C4-N, by extending the conjugation of a Y5 molecule with a naphthalenebased end acceptor. In comparison with Y5-based devices, PM6:BTP-C2C4-N-based devices exhibited significantly higher J(sc) of 18.2 mA cm(-2) followed by a high V-oc. To further increase the photovoltaic properties of BTP-C2C4-N analogues, BTP-C4C6-N and BTP-C6C8-N molecules with better processability and film morphology are obtained by adjusting the alkyl branched chain length. The optimized OSCs based on BTP-C4C6-N with a moderate alkyl branched chain length exhibited the best PCE of 12.4% with a high V-oc of 0.94 V and J(sc) of 20.7 mA cm(-2). Notably, the devices achieved a low energy loss of 0.49 eV (0.51 eV for Y5 system) accompanied by a small nonradiative energy loss. The results indicate that nonfullerene acceptors with extended terminal motifs and optimized branched chain lengths can effectively enhance the performance of OSCs and reduce energy loss.
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| 5. |
- Qi, Zhenyu, et al.
(författare)
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Blueshifting the Absorption of a Small -Molecule Donor and Using it as the Third Component to Achieve High-Efficiency Ternary Organic Solar Cells
- 2022
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Ingår i: Solar RRL. - : WILEY-V C H VERLAG GMBH. - 2367-198X. ; 6:9
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Tidskriftsartikel (refereegranskat)abstract
- Adding a small-molecule donor (SMD) to state-of-the-art nonfullerene organic solar cells (OSCs) is demonstrated as a useful strategy to construct ternary organic solar cells, as SMDs typically have high crystallinity and can tune charge transport properties of OSCs. However, the absorption of most SMDs overlaps with typical donor polymers (e.g., PM6), which is against the general guidelines of adopting materials with complementary absorption in ternary OSCs. Herein, the absorption of state-of-art SMDs (BTR-CI) by linking the beta position of the outer thiophene to the alpha position of the inner thiophene unit is intentionally blueshifted. The resulting molecule beta-S1 shows a maximum absorption peak at 505 nm in the film state, which exhibits wider bandgap and shows complementary absorption with the host system (PM6:Y6). The corresponding ternary OSCs with 20%wt beta-S1 show significantly enhanced efficiency from 16.2% to 17.1% due to the increased short-circuit current (J(sc)) and improved fill factor (FF). Herein, an effective strategy to design SMDs with both wider bandgaps and higher crystallinity for high-performance ternary OSCs is presented.
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| 6. |
- Sun, Huiliang, et al.
(författare)
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A Narrow-Bandgap n-Type Polymer with an Acceptor-Acceptor Backbone Enabling Efficient All-Polymer Solar Cells
- 2020
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Ingår i: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Narrow-bandgap polymer semiconductors are essential for advancing the development of organic solar cells. Here, a new narrow-bandgap polymer acceptor L14, featuring an acceptor-acceptor (A-A) type backbone, is synthesized by copolymerizing a dibrominated fused-ring electron acceptor (FREA) with distannylated bithiophene imide. Combining the advantages of both the FREA and the A-A polymer, L14 not only shows a narrow bandgap and high absorption coefficient, but also low-lying frontier molecular orbital (FMO) levels. Such FMO levels yield improved electron transfer character, but unexpectedly, without sacrificing open-circuit voltage (V-oc), which is attributed to a small nonradiative recombination loss (E-loss,E-nr) of 0.22 eV. Benefiting from the improved photocurrent along with the high fill factor andV(oc), an excellent efficiency of 14.3% is achieved, which is among the highest values for all-polymer solar cells (all-PSCs). The results demonstrate the superiority of narrow-bandgap A-A type polymers for improving all-PSC performance and pave a way toward developing high-performance polymer acceptors for all-PSCs.
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| 7. |
- Yao, Huatong, et al.
(författare)
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All-Polymer Solar Cells with over 12% Efficiency and a Small Voltage Loss Enabled by a Polymer Acceptor Based on an Extended Fused Ring Core
- 2020
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Although the field of all-polymer solar cells (all-PSCs) has seen rapid progress in device efficiencies during the past few years, there are limited choices of polymer acceptors that exhibit strong absorption in the near-IR region and achieve high open-circuit voltage (V-OC) at the same time. In this paper, an all-PSC device is demonstrated with a 12.06% efficiency based on a new polymer acceptor (named PT-IDTTIC) that exhibits strong absorption (maximum absorption coefficient: 2.41 x 10(5)cm(-1)) and a narrow optical bandgap (1.49 eV). Compared to previously reported polymer acceptors such as those based on the indacenodithiophene (IDT) core, the indacenodithienothiophene (IDTT) core has further extended fused ring, providing the polymer with extended absorption into the near-IR region and also increases the electron mobility of the polymer. By blending PT-IDTTIC with the donor polymer, PM6, a high-efficiency all-PSC is achieved with a small voltage loss of 0.52 V, without sacrificingJ(SC)and FF, which demonstrates the great potential of high-performance all-PSCs.
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| 8. |
- Yu, Han, et al.
(författare)
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Fluorinated End Group Enables High-Performance All-Polymer Solar Cells with Near-Infrared Absorption and Enhanced Device Efficiency over 14%
- 2021
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Fluorination of end groups has been a great success in developing efficient small molecule acceptors. However, this strategy has not been applied to the development of polymer acceptors. Here, a dihalogenated end group modified by fluorine and bromine atoms simultaneously, namely IC-FBr, is first developed, then employed to construct a new polymer acceptor (named PYF-T) for all-polymer solar cells (all-PSCs). In comparison with its non-fluorinated counterpart (PY-T), PYF-T exhibits stronger and red-shifted absorption spectra, stronger molecular packing and higher electron mobility. Meanwhile, the fluorination on the end groups down-shifts the energy levels of PYF-T, which matches better with the donor polymer PM6, leading to efficient charge transfer and small voltage loss. As a result, an all-PSC based on PM6:PYF-T yields a higher power conversion efficiency (PCE) of 14.1% than that of PM6:PY-T (11.1%), which is among the highest values for all-PSCs reported to date. This work demonstrates the effectiveness of fluorination of end-groups in designing high-performance polymer acceptors, which paves the way toward developing more efficient and stable all-PSCs.
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| 9. |
- Fu, Huiting, et al.
(författare)
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High Efficiency (15.8%) All-Polymer Solar Cells Enabled by a Regioregular Narrow Bandgap Polymer Acceptor
- 2021
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 143:7, s. 2665-2670
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Tidskriftsartikel (refereegranskat)abstract
- Y Despite the significant progresses made in all-polymer solar cells (all-PSCs) recently, the relatively low short-circuit current density (J(sc)) and large energy loss are still quite difficult to overcome for further development. To address these challenges, we developed a new class of narrow-bandgap polymer acceptors incorporating a benzotriazole (BTz)-core fused-ring segment, named the PZT series. Compared to the commonly used benzothiadiazole (BT)-containing polymer PYT, the less electron-deficient BTz renders PZT derivatives with significantly red-shifted optical absorption and up-shifted energy levels, leading to simultaneously improved J(sc) and open-circuit voltage in the resultant all-PSCs. More importantly, a regioregular PZT (PZT-gamma) has been developed to achieve higher regiospecificity for avoiding the formation of isomers during polymerization. Benefiting from the more extended absorption, better backbone ordering, and more optimal blend morphology with donor component, PZT-gamma-based all-PSCs exhibit a record-high power conversion efficiency of 15.8% with a greatly enhanced J(sc) of 24.7 mA/cm(2) and a low energy loss of 0.51 eV.
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| 10. |
- Gao, Yanhong, et al.
(författare)
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Quantification of the relative role of land-surface processes and large-scale forcing in dynamic downscaling over the Tibetan Plateau
- 2017
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 48:5, s. 1705-1721
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 Springer-Verlag Berlin HeidelbergDynamical downscaling modeling (DDM) is important to understand regional climate change and develop local mitigation strategies, and the accuracy of DDM depends on the physical processes involved in the regional climate model as well as the forcing datasets derived from global models. This study investigates the relative role of the land surface schemes and forcing datasets in the DDM over the Tibet Plateau (TP), a region complex in topography and vulnerable to climate change. Three Weather Research and Forecasting model dynamical downscaling simulations configured with two land surface schemes [Noah versus Noah with multiparameterization (Noah-MP)] and two forcing datasets are performed over the period of 1980–2005. The downscaled temperature and precipitation are evaluated with observations and inter-compared regarding temporal trends, spatial distributions, and climatology. Results show that the temporal trends of the temperature and precipitation are determined by the forcing datasets, and the forcing dataset with the smallest trend bias performs the best. Relative to the forcing datasets, land surface processes play a more critical role in the DDM over the TP due to the strong heating effects on the atmospheric circulation from a vast area at exceptionally high elevations. By changing the vertical profiles of temperature in the atmosphere and the horizontal patterns of moisture advection during the monsoon seasons, the land surface schemes significantly regulate the downscaled temperature and precipitation in terms of climatology and spatial patterns. This study emphasizes the selection of land surface schemes is of crucial importance in the successful DDM over the TP.
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| 11. |
- 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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| 12. |
- Jiang, Kui, et al.
(författare)
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Suppressed recombination loss in organic photovoltaics adopting a planar-mixed heterojunction architecture
- 2022
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Ingår i: Nature Energy. - : NATURE PORTFOLIO. - 2058-7546. ; 7:11, s. 1076-1086
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Tidskriftsartikel (refereegranskat)abstract
- At present, high-performance organic photovoltaics mostly adopt a bulk-heterojunction architecture, in which exciton dissociation is facilitated by charge-transfer states formed at numerous donor-acceptor (D-A) heterojunctions. However, the spin character of charge-transfer states originated from recombination of photocarriers allows relaxation to the lowest-energy triplet exciton (T-1) at these heterojunctions, causing photocurrent loss. Here we find that this loss pathway can be alleviated in sequentially processed planar-mixed heterojunction (PMHJ) devices, employing donor and acceptor with intrinsically weaker exciton binding strengths. The reduced D-A intermixing in PMHJ alleviates non-geminate recombination at D-A contacts, limiting the chance of relaxation, thus suppressing T-1 formation without sacrificing exciton dissociation efficiency. This resulted in devices with high power conversion efficiencies of >19%. We elucidate the working mechanisms for PMHJs and discuss the implications for material design, device engineering and photophysics, thus providing a comprehensive grounding for future organic photovoltaics to reach their full promise. Organic solar cells with a bulk-heterojunction architecture suffer from photocurrent loss driven by triplet states. Now, Jiang et al. show that sequentially deposited donor-acceptor planar-mixed heterojunctions suppress triplet formation, enabling efficiencies over 19%.
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| 13. |
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| 14. |
- Lee, Cheng-Ruei, et al.
(författare)
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Young inversion with multiple linked QTLs under selection in a hybrid zone
- 2017
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Ingår i: NATURE ECOLOGY & EVOLUTION. - : Springer Science and Business Media LLC. - 2397-334X. ; 1:5
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Tidskriftsartikel (refereegranskat)abstract
- Fixed chromosomal inversions can reduce gene flow and promote speciation in two ways: by suppressing recombination and by carrying locally favoured alleles at multiple loci. However, it is unknown whether favoured mutations slowly accumulate on older inversions or if young inversions spread because they capture pre-existing adaptive quantitative trait loci (QTLs). By genetic mapping, chromosome painting and genome sequencing, we have identified a major inversion controlling ecologically important traits in Boechera stricta. The inversion arose since the last glaciation and subsequently reached local high frequency in a hybrid speciation zone. Furthermore, the inversion shows signs of positive directional selection. To test whether the inversion could have captured existing, linked QTLs, we crossed standard, collinear haplotypes from the hybrid zone and found multiple linked phenology QTLs within the inversion region. These findings provide the first direct evidence that linked, locally adapted QTLs may be captured by young inversions during incipient speciation.
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| 15. |
- Li, Xiane, et al.
(författare)
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Mapping the energy level alignment at donor/acceptor interfaces in non-fullerene organic solar cells
- 2022
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Ingår i: Nature Communications. - : Nature Portfolio. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Energy level alignment (ELA) at donor-acceptor heterojunctions is of vital importance yet largely undetermined in organic solar cells. Here, authors determine the heterojunction ELA with (mono) layer-by-layer precision to understand the co-existence of efficient charge. Energy level alignment (ELA) at donor (D) -acceptor (A) heterojunctions is essential for understanding the charge generation and recombination process in organic photovoltaic devices. However, the ELA at the D-A interfaces is largely underdetermined, resulting in debates on the fundamental operating mechanisms of high-efficiency non-fullerene organic solar cells. Here, we systematically investigate ELA and its depth-dependent variation of a range of donor/non-fullerene-acceptor interfaces by fabricating and characterizing D-A quasi bilayers and planar bilayers. In contrast to previous assumptions, we observe significant vacuum level (VL) shifts existing at the D-A interfaces, which are demonstrated to be abrupt, extending over only 1-2 layers at the heterojunctions, and are attributed to interface dipoles induced by D-A electrostatic potential differences. The VL shifts result in reduced interfacial energetic offsets and increased charge transfer (CT) state energies which reconcile the conflicting observations of large energy level offsets inferred from neat films and large CT energies of donor - non-fullerene-acceptor systems.
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| 16. |
- Liang, Lin, et al.
(författare)
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Non-Interpenetrated Single-Crystal Covalent Organic Frameworks
- 2020
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:41, s. 17991-17995
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Tidskriftsartikel (refereegranskat)abstract
- Growth of covalent organic frameworks (COFs) as single crystals is extremely challenging. Inaccessibility of open-structured single-crystal COFs prevents the exploration of structure-oriented applications. Herein we report for the first time a non-interpenetrated single-crystal COF, LZU-306, which possesses the open structure constructed exclusively via covalent assembly. With a high void volume of 80 %, LZU-306 was applied to investigate the intrinsic dynamics of reticulated tetraphenylethylene (TPE) as the individual aggregation-induced-emission moiety. Solid-state(2)H NMR investigation has determined that the rotation of benzene rings in TPE, being the freest among the reported cases, is as fast as 1.0x10(4) Hz at 203 K to 1.5x10(7) Hz at 293 K. This research not only explores a new paradigm for single-crystal growth of open frameworks, but also provides a unique matrix-isolation platform to reticulate functional moieties into a well-defined and isolated state.
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| 17. |
- Liu, Tao, et al.
(författare)
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16% efficiency all-polymer organic solar cells enabled by a finely tuned morphology via the design of ternary blend
- 2021
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Ingår i: Joule. - : CELL PRESS. - 2542-4351. ; 5:4, s. 914-930
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Tidskriftsartikel (refereegranskat)abstract
- A SUMMARY There is an urgent demand for all-polymer organic solar cells (AP-OSCs) to gain higher efficiency. Here, we successfully improve the performance to 16.09% by introducing a small amount of BN-T, a B <- N-type polymer acceptor, into the PM6:PY-IT blend. It has been found that BN-T makes the active layer, based on the PM6:PY-IT:BN-T ternary blend, more crystalline but meanwhile slightly reduces the phase separation, leading to enhancement of both exciton harvesting and charge transport. From a thermodynamic viewpoint, BN-T prefers to reside between PM6 and PY-IT, and the fraction of this fine-tunes the morphology. Besides, a significantly reduced nonradiative energy loss occurs in the ternary blend, along with the coexistence of energy and charge transfer between the two acceptors. The progressive performance facilitated by these improved properties demonstrates that AP-OSCs can possibly comparably efficient with those based on small molecule acceptors, further enhancing the competitiveness of this device type.
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| 18. |
- Liu, Yizhong, et al.
(författare)
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A Blockchain-Based Cross-Domain Authentication Management System for IoT Devices
- 2024
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Ingår i: IEEE Transactions on Network Science and Engineering. - Piscataway, NJ : IEEE Computer Society. - 2327-4697. ; 11:1, s. 115-127
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Tidskriftsartikel (refereegranskat)abstract
- With the emergence of the resource and equipment sharing concept, many enterprises and organizations begin to implement cross-domain sharing of devices, especially in the field of the Internet of Things (IoT). However, there are many problems in the cross-domain usage process of devices, such as access control, authentication, and privacy protection. In this paper, we make the following contributions. First, we propose a blockchain-based cross-domain authentication management system for IoT devices. The sensitive device information is stored in a Merkle tree structure where only the Merkle root is uploaded to the smart contract. Second, a detailed security and performance analysis is given. We prove that our system is secure against several potential security threats and satisfies validity and liveness. Compared to existing schemes, our schemes realize decentralization, privacy, scalability, fast off-chain authentication, and low on-chain storage. Third, we implement the system on Ethereum with varying parameters known as domain number, concurrent authentication request number, and Merkle tree leaf number. Experimental results show that our solution supports the management of millions of devices in a domain and can process more than 10,000 concurrent cross-domain authentication requests, consuming only 5531 ms. Meanwhile, the gas costs are shown to be acceptable. © IEEE
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| 19. |
- Luo, Zhenghui, et al.
(författare)
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Fine-Tuning Energy Levels via Asymmetric End Groups Enables Polymer Solar Cells with Efficiencies over 17%
- 2020
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Ingår i: Joule. - : CELL PRESS. - 2542-4351. ; 4:6, s. 1236-1247
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Tidskriftsartikel (refereegranskat)abstract
- Generally, it is important to fine-tune the energy levels of donor and acceptor materials in the field of polymer solar cell (PSCs) to achieve a minimal highest occupied molecular orbital (HOMO) energy offset, which yet is still sufficient for charge separation. Based on the high-performance small-molecule acceptor (SMA) of BTP-4F, we modified the end groups of BTP-4F from IC-2F to CPTCN-Cl. It was found that when both end groups were substituted by CPTCN-Cl, the energy level upshift was too large that caused unfavorable energetic alignment, thus poor device performance. By using the strategy of asymmetric end groups, we were able to achieve near optimal energy level match, resulting in higher open-circuit voltage (V-OC) and power conversion efficiency (PCE) compared with those given by the PM6:BTP-4F system. Our strategy can be useful and potentially applied to othermaterial systems for maximizing efficiency of non-fullerene PSCs.
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| 20. |
- Luo, Zhenghui, et al.
(författare)
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Heteroheptacene-based acceptors with thieno[3,2-b]pyrrole yield high-performance polymer solar cells
- 2022
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Ingår i: NATIONAL SCIENCE REVIEW. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 9:7
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Tidskriftsartikel (refereegranskat)abstract
- Rationally utilizing and developing synthetic units is of particular significance for the design of high-performance non-fullerene small-molecule acceptors (SMAs). Here, a thieno[3,2-b]pyrrole synthetic unit was employed to develop a set of SMAs (ThPy1, ThPy2, ThPy3 and ThPy4) by changing the number or the position of the pyrrole ring in the central core based on a standard SMA of IT-4Cl, compared to which the four thieno[3,2-b]pyrrole-based acceptors exhibit bathochromic absorption and upshifted frontier orbital energy level due to the strong electron-donating ability of pyrrole. As a result, the polymer solar cells (PSCs) of the four thieno[3,2-b]pyrrole-based acceptors yield higher open-circuit voltage and lower energy loss relative to those of the IT-4Cl-based device. What is more, the ThPy3-based device achieves a power conversion efficiency (PCE) (15.3%) and an outstanding fill factor (FF) (0.771) that are superior to the IT-4Cl-based device (PCE = 12.6%, FF = 0.758). The ThPy4-based device realizes the lowest energy loss and the smallest optical band gap, and the ternary PSC device based on PM6:BTP-eC9:ThPy4 exhibits a PCE of 18.43% and a FF of 0.802. Overall, this work sheds light on the great potential of thieno[3,2-b]pyrrole-based SMAs in realizing low energy loss and high PCE. Four heteroheptacene-based acceptors using thieno[3,2-b]pyrrole building block were developed for the first time, and all the four acceptors-based devices realized high performance and low energy loss.
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| 21. |
- Ma, Ruijie, et al.
(författare)
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All-polymer solar cells with over 16% efficiency and enhanced stability enabled by compatible solvent and polymer additives
- 2022
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Ingår i: Aggregate. - : Wiley. - 2692-4560 .- 2766-8541. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Considering the robust and stable nature of the active layers, advancing the power conversion efficiency (PCE) has long been the priority for all-polymer solar cells (all-PSCs). Despite the recent surge of PCE, the photovoltaic parameters of the state-of-the-art all-PSC still lag those of the polymer:small molecule-based devices. To compete with the counterparts, judicious modulation of the morphology and thus the device electrical properties are needed. It is difficult to improve all the parameters concurrently for the all-PSCs with advanced efficiency, and one increase is typically accompanied by the drop of the other(s). In this work, with the aids of the solvent additive (1-chloronaphthalene) and the n-type polymer additive (N2200), we can fine-tune the morphology of the active layer and demonstrate a 16.04% efficient all-PSC based on the PM6:PY-IT active layer. The grazing incidence wide-angle X-ray scattering measurements show that the shape of the crystallites can be altered, and the reshaped crystallites lead to enhanced and more balanced charge transport, reduced recombination, and suppressed energy loss, which lead to concurrently improved and device efficiency and stability.
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| 22. |
- Qian, Deping, et al.
(författare)
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Correlating the Hybridization of Local-Exciton and Charge-Transfer States with Charge Generation in Organic Solar Cells
- 2023
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- In organic solar cells with very small energetic-offset (& UDelta;ELE - CT), the charge-transfer (CT) and local-exciton (LE) states strongly interact via electronic hybridization and thermal population effects, suppressing the non-radiative recombination. Here, we investigated the impact of these effects on charge generation and recombination. In the blends of PTO2:C8IC and PTO2:Y6 with very small, ultra-fast CT state formation was observed, and assigned to direct photoexcitation resulting from strong hybridization of the LE and CT states (i.e., LE-CT intermixed states). These states in turn accelerate the recombination of both CT and charge separated (CS) states. Moreover, they can be significantly weakened by an external-electric field, which enhanced the yield of CT and CS states but attenuated the emission of the device. This study highlights that excessive LE-CT hybridization due to very low , whilst enabling direct and ultrafast charge transfer and increasing the proportion of radiative versus non-radiative recombination rates, comes at the expense of accelerating recombination losses competing with exciton-to-charge conversion process, resulting in a loss of photocurrent generation.
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| 23. |
- Qin, Linqing, et al.
(författare)
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Triplet Acceptors with a D-A Structure and Twisted Conformation for Efficient Organic Solar Cells
- 2020
-
Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 59:35, s. 15043-15049
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Tidskriftsartikel (refereegranskat)abstract
- Triplet acceptors have been developed to construct high-performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T-1) are close to those of charge-transfer states ((CT)-C-3). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large pi-conjugated core and D-A structure, were confirmed to be triplet materials, leading to high-performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin-orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T-1 is close to (CT)-C-3, facilitating the split of triplet exciton to free charges.
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| 24. |
- Shi, Yanan, et al.
(författare)
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Optimizing the Charge Carrier and Light Management of Nonfullerene Acceptors for Efficient Organic Solar Cells with Small Nonradiative Energy Losses
- 2021
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Ingår i: Solar RRL. - : WILEY-V C H VERLAG GMBH. - 2367-198X. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- The photovoltaic properties and energy losses of organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) are highly dependent on their molecular structures and aggregation morphologies. Charge carrier and light managements are important to optimize NFA molecules. Herein, four NFAs with different alkyl substituents and end groups, named BTP-C11-N2F, BTP-C9-N2F, BTP-C9-IC4F, and BTP-C9-N4F, are designed and synthesized by side-chain shortening, end-acceptor pi-extension, and fluorination. As a result, a favorable morphology is achieved in BTP-C9-N4F-based OSCs by using typical high bandgap polymer PM6 as a donor, and this system obtains the highest power conversion efficiency of 17.0% with a short circuit current (J(sc)) of 26.3 mA cm(-2), an open circuit current (V-oc) of 0.85 V, and a fill factor (FF) of 75.7%. In addition, its light (J(sc)) and charge carrier (V-oc x FF) managements relative to the Shockley-Queisser limit are also increased. Extending the conjugation of the end groups increased the energy levels of NFAs and enabled an E-loss of 0.50 eV with a nonradiative recombination loss of as low as 0.20 eV in BTP-C11-N2F-based OSCs. This work provides an efficient strategy to optimize the molecular structures of nonfullerene acceptors and further improve the properties of OSCs.
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| 25. |
- Sun, Huiliang, et al.
(författare)
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A monothiophene unit incorporating both fluoro and ester substitution enabling high-performance donor polymers for non-fullerene solar cells with 16.4% efficiency
- 2019
-
Ingår i: Energy & Environmental Science. - : ROYAL SOC CHEMISTRY. - 1754-5692 .- 1754-5706. ; 12:11, s. 3328-3337
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Tidskriftsartikel (refereegranskat)abstract
- Thiophene and its derivatives have been extensively used in organic electronics, particularly in the field of polymer solar cells (PSCs). Significant research efforts have been dedicated to modifying thiophene-based units by attaching electron-donating or withdrawing groups to tune the energy levels of conjugated materials. Herein, we report the design and synthesis of a novel thiophene derivative, FE-T, featuring a monothiophene functionalized with both an electron-withdrawing fluorine atom (F) and an ester group (E). The FE-T unit possesses distinctive advantages of both F and E groups, the synergistic effects of which enable significant downshifting of the energy levels and enhanced aggregation/crystallinity of the resulting organic materials. Shown in this work are a series of polymers obtained by incorporating the FE-T unit into a PM6 polymer to fine-tune the energetics and morphology of this high-performance PSC material. The optimal polymer in the series shows a downshifted HOMO and an improved morphology, leading to a high PCE of 16.4% with a small energy loss (0.53 eV) enabled by the reduced non-radiative energy loss (0.23 eV), which are among the best values reported for non-fullerene PSCs to date. This work shows that the FE-T unit is a promising building block to construct donor polymers for high-performance organic photovoltaic cells.
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| 26. |
- Sun, Huiliang, et al.
(författare)
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Reducing energy loss via tuning energy levels of polymer acceptors for efficient all-polymer solar cells
- 2020
-
Ingår i: Science China Chemistry. - : Springer Science and Business Media LLC. - 1869-1870 .- 1674-7291. ; 63:12, s. 1785-1792
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Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage (Voc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limiting Voc and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a large Voc of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with large Voc and drives the further development of all-PSCs.
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| 27. |
- Sun, Huiliang, et al.
(författare)
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Reducing energy lossviatuning energy levels of polymer acceptors for efficient all-polymer solar cells
- 2020
-
Ingår i: Science China Chemistry. - : Science China Press and Springer-Verlag GmbH Germany. - 1674-7291 .- 1869-1870. ; 63, s. 1785-1792
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Tidskriftsartikel (refereegranskat)abstract
- The open-circuit voltage (V-oc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limitingV(oc)and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a largeV(oc)of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with largeV(oc)and drives the further development of all-PSCs.
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| 28. |
- Sun, Xiaoyu, et al.
(författare)
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Revealing microstructural degradation mechanism induced by interdiffusion between Amdry365 coating and IN792 superalloy
- 2024
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Ingår i: Materials & design. - : ELSEVIER SCI LTD. - 0264-1275 .- 1873-4197. ; 241
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Metallic coatings are widely employed to improve the oxidation resistance of superalloys. However, the interdiffusion between the metallic coatings and the superalloys leads to microstructural degradation in both. Some of the underlying degradation mechanisms are still elusive, e.g., the γ′ (Ni3Al) phase depletion in superalloys, where a large amount of γ′ precipitates are dissolved in the γ matrix even though the incoming Al from coatings indeed increases the Al content. Here, we investigated the interdiffusion behavior between the Amdry365 coating and the IN792 superalloy at 1100 °C, using multiple microscopic techniques and thermodynamics calculations. Our results showed an excellent agreement between experiments and thermodynamics simulations, indicating the dominant role of Al on the initial diffusion-induced phase transitions. We proposed the Al-Cr interference effect to account for the pile-up behavior of Cr and the reduced Al content near the coating/superalloy interface. The local phase equilibrium calculations revealed that the γ′ depletion in the superalloy is primarily attributed to the loss of γ′-forming elements, such as Ta and Ti. Our findings opened up an avenue for studies on the superalloy/coating interdiffusion, contributing to reducing this damaging impact.
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| 29. |
- Sun, Xiaoyu, et al.
(författare)
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Revealing microstructural degradation mechanism induced by interdiffusion between Amdry365 coating and IN792 superalloy
- 2024
-
Ingår i: Materials and Design. - : ELSEVIER SCI LTD. - 1873-4197 .- 0264-1275. ; 241
-
Tidskriftsartikel (refereegranskat)abstract
- Metallic coatings are widely employed to improve the oxidation resistance of superalloys. However, the interdiffusion between the metallic coatings and the superalloys leads to microstructural degradation in both. Some of the underlying degradation mechanisms are still elusive, e.g., the γ′ (Ni3Al) phase depletion in superalloys, where a large amount of γ′ precipitates are dissolved in the γ matrix even though the incoming Al from coatings indeed increases the Al content. Here, we investigated the interdiffusion behavior between the Amdry365 coating and the IN792 superalloy at 1100 °C, using multiple microscopic techniques and thermodynamics calculations. Our results showed an excellent agreement between experiments and thermodynamics simulations, indicating the dominant role of Al on the initial diffusion-induced phase transitions. We proposed the Al-Cr interference effect to account for the pile-up behavior of Cr and the reduced Al content near the coating/superalloy interface. The local phase equilibrium calculations revealed that the γ′ depletion in the superalloy is primarily attributed to the loss of γ′-forming elements, such as Ta and Ti. Our findings opened up an avenue for studies on the superalloy/coating interdiffusion, contributing to reducing this damaging impact.
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| 30. |
- Tang, Yumin, et al.
(författare)
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Two Compatible Polymer Donors Enabling Ternary Organic Solar Cells with a Small Nonradiative Energy Loss and Broad Composition Tolerance
- 2020
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Ingår i: Solar RRL. - : Wiley-VCH Verlagsgesellschaft. - 2367-198X. ; 4:11
-
Tidskriftsartikel (refereegranskat)abstract
- High-performance nonfullerene ternary organic solar cells (OSCs) with two polymer donors are less frequently reported because of the limited numbers of efficient polymer donors with good compatibility. Herein, a wide-bandgap polymer P1 with a deep-lying highest occupied molecular orbital (HOMO) level is incorporated as the third component into the benchmark PM6:Y6 binary system to fabricate ternary OSCs. The introduction of P1 not only leads to extended absorption coverage and forms a cascade-like energy level alignment but also shows excellent compatibility with PM6, resulting in a favorable morphology in the ternary blend. More importantly, P1 possesses a deeper HOMO level (-5.6 eV) than most well-known donor polymers, which enables resulting ternary OSCs with an improved open-circuit voltage. As a result, the optimized ternary OSCs with 40 wt% P1 in donors achieve a power conversion efficiency (PCE) of 16.2% with a small nonradiative recombination loss of 0.23 eV, which is among the highest values of ternary OSCs based on two polymer donors. In addition, the ternary OSCs show a broad composition tolerance with a high PCE of over 14% throughout the whole blend ratios. These results provide an effective approach to fabricate efficient ternary OSCs by synergizing two wide-bandgap polymer donors.
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| 31. |
- Wang, Yuming, et al.
(författare)
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Origins of the open-circuit voltage in ternary organic solar cells and design rules for minimized voltage losses
- 2023
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Ingår i: Nature Energy. - : NATURE PORTFOLIO. - 2058-7546. ; 8:9, s. 978-988
-
Tidskriftsartikel (refereegranskat)abstract
- The power conversion efficiency of ternary organic solar cells (TOSCs), consisting of one host binary blend and one guest component, remains limited by large voltage losses. The fundamental understanding of the open-circuit voltage (V-OC) in TOSCs is controversial, limiting rational design of the guest component. In this study, we systematically investigate how the guest component affects the radiative and non-radiative related parts of V-OC of a series of TOSCs using the detailed balanced principle. We highlight that the thermal population of charge-transfer and local exciton states provided by the guest binary blend (that is, the guest-component-based binary blend) has a significant influence on the non-radiative voltage losses. Ultimately, we provide two design rules for enhancing the V-OC in TOSCs: high emission yield for the guest binary blend and similar charge-transfer-state energies for host/guest binary blends; high miscibility of the guest component with the low gap component in the host binary blend. The performance of ternary organic solar cells is limited by voltage losses. Using the detailed balance principle, Wang et al. show how the third component of the blend affects the open-circuit voltage and delineate molecular design rules.
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| 32. |
- Wei, Yanan, et al.
(författare)
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A universal method for constructing high efficiency organic solar cells with stacked structures
- 2021
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Ingår i: Energy & Environmental Science. - : ROYAL SOC CHEMISTRY. - 1754-5692 .- 1754-5706. ; 14:4, s. 2314-2321
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Tidskriftsartikel (refereegranskat)abstract
- The construction of organic solar cells with stacked structures by the sequential deposition (SD) of donor and acceptor films has great potential in industrial production, as it demonstrates little dependence on the ratio of donor and acceptor materials, solvents, and additives. Herein, we present an eco-friendly solvent protection (ESP) method for the fabrication of high-performance OSCs with stacked structures. Several non-aromatic and non-halogenated solvents are employed as protective agents to build SD devices with a configuration of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS Clevios P VP Al 4083)/donor/protective solvent/acceptor/perylene diimide functionalized with amino N-oxide (PDINO)/Al, which shows that n-octane is the optimal choice for SD devices. Nine different SD systems including the fullerene and nonfullerene ones present comparable photovoltaic performance to their BC counterparts, which proves the universality of this ESP method. Significantly, the device of ITO/PEDOT:PSS/D18/N3/PDINO/Al with n-octane as the protective solvent achieves a maximum PCE of 17.52%, which is the record efficiency of SD devices. Furthermore, a protective factor (delta) is proposed to demonstrate the quantitative relationship between delta and PCE after experimental and theoretical investigation, which presents an idea to understand the mechanism and provides a guideline for solvent choices.
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| 33. |
- Yu, Hongxiao, et al.
(författare)
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Robotic wheeled vehicle ripple tentacles motion planning method
- 2012
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Ingår i: Intelligent Vehicles Symposium (IV), 2012 IEEE. - Piscataway, N.J. : IEEE Press. - 9781467321198 ; , s. 1156-1161
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Konferensbidrag (refereegranskat)abstract
- This paper describes a nonholonomic robotic wheeled vehicle ripple tentacle motion planning method, aiming to improve the vehicle's trajectory smoothness and avoid frequent weight parameters adjustment in different environments. In the regular tentacle motion planning algorithm, the planning result is selected among the drivable tentacles using a weighted sum cost function. Though the method is simple and easy to understand, it is difficult to adjust the weighted coefficients in different environments. To solve this problem, a geometrical ripple tentacles technique is used to choose a tentacle as a sub-optimal path. Compared with the regular tentacles algorithm, the proposed ripple tentacle algorithm can get a better performance in vehicle's trajectory smoothness with an acceptable runtime expense. And another two traits can also distinguish this method: (a) it can avoid weight parameter adjustment in different environments and varied vehicle's states, and (b) it can be used in both unknown environment and partly known environment with goal point and global reference path. In the totally unknown environment, it acts as a pure obstacle avoidance algorithm, and when there is a global path, it can follow the reference path and avoid hazards simultaneously. © 2012 IEEE.
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| 34. |
- Yu, Jianwei, 1992-
(författare)
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The Influence of Energy Levels on Voltage Losses and Charge Generation in Organic Solar Cells
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic solar cells (OSCs) are a next-generation photovoltaic technology that convert solar energy to electrical energy. They have attracted great attention due to their advantages of low cost, ease of synthesis, light weight, mechanical flexibility, and roll-to-roll processability. In the past decades, owing to the development of the materials, device optimization and the understanding of the working mechanism, the power conversion efficiency (PCE) has been boosted to ~19%. However, the efficiency of the OSCs is still not comparable to the conventional inorganic solar cells and emerging perovskite solar cells due to the large open-circuit voltage loss (Vloss). In addition, it is also important to obtain efficient charge generation while reducing the Vloss. Thus, understanding the loss mechanisms in the OSCs is significant for achieving further improvement.In this thesis, a novel small-molecule donor named ZR1 was used to fabricate all-small-molecule OSCs (SM-OSCs), which shows efficient charge separation and transport with the optimized hierarchical morphologies, obtaining a breakthrough efficiency of 13.34% with a low Vloss (0.54 eV) in SM-OSCs. In this system, the energy offsets between the donor and acceptor (ΔHOMO or ΔLUMO) play an important role in the open-circuit voltage (VOC) of the OSCs. According to the optoelectronic reciprocity introduced in this thesis, the sub-gap absorption and emission by charge transfer (CT) states lead to large radiative and non-radiative recombination losses. The results show that the decreased HOMO offsets between donor and acceptor can effectively reduce both radiative and non-radiative recombination losses from the CT states, resulting in a suppressed Vloss.In addition to the SM-OSCs, we also study the Vloss and charge generation in the all-polymer OSCs (all- PSCs). A series of polymer acceptors were designed and applied in all-PSCs. In this work, all devices with negligible LUMO offsets show high VOCs of 1.02-1.15 V and good short-circuit currents (JSCs) of 8.87-15.16 mA cm−2 as well as small Vlosss. This study reveals that the small Vloss and the effective charge generation can also be realized simultaneously in all-PSCs with small energy offsets.Next, we found that introducing a third component can also reduce Vloss. In this work, we start with the fundamental photophysical processes which determine the VOCs of the devices and provide a universal approach framework well explaining the VOC of ternary OSCs (TOSCs) in different situations. By combining experimental investigations with theoretical simulations, we highlight the significant influence of the thermal population arising from the guest component-related CT states and local excited (LE)states on the non-radiative recombination losses in TOSCs. Firmly based on our new understanding, we provide design rules for enhancing the VOC in TOSCs: 1) high emission yield for the guest binary system; close charge-transfer energies between two binary systems; 2) high miscibility of the guest component with the low-optical-gap component in the host binary blends.In the all-PSCs work we did before, we find the small Vloss and the effective charge generation can be achieved simultaneously with small energy offsets, which can be also observed in other non-fullerene based OSCs. It was found that some of non-fullerene acceptors based OSCs can realize an efficient charge generation and a suppressed charge recombination process with small energy offsets (< 0.3 eV) between the donor and the acceptor, leading to a low Vloss, a high JSC, and a high fill factor (FF) simultaneously. Here, we investigate a series of OSCs blends with different HOMO offsets between donor and in a large range of ~ 0 to 0.50 eV. Along with decreasing HOMO offsets, the blends show reduced Vlosss. For the JSC and the FF, we observe a maximum value at an optimal energetic offset around 0.2-0.3 eV and the optimal energetic offset appears at different values for different non-fullerene acceptors. Through the analysis of the ultrafast transient absorption, we find inefficient charge generation when the HOMO offset is close to zero, which attributed to the back transfer of a hole from the donor to the acceptor. The affected charge generation at the small HOMO offsets is probably the main reason for the deceased JSC and FF. This study demonstrates the existence of optimal energy offsets for achieving high-performance OSCs.
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| 35. |
- Zhang, Xin, et al.
(författare)
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Enhancing the Photovoltaic Performance of Triplet Acceptors Enabled by Side-Chain Engineering
- 2021
-
Ingår i: Solar RRL. - : WILEY-V C H VERLAG GMBH. - 2367-198X. ; 5:10
-
Tidskriftsartikel (refereegranskat)abstract
- Triplet excitons have both longer lifetimes and diffusion lengths than singlet excitons due to the nature of triplet excitons, which is expected to increase the photocurrent and further improve the performance of organic solar cells (OSCs). However, the working mechanism of triplet excitons in OSCs is not clearly clarified. Therefore, it is urgent to develop new triplet acceptors for in-depth understanding. Herein, a series of acceptors (BTn-4Cl) are synthesized by fine-tuning of the side-chain branch positions. The generation of triplet excitons of BTn-4Cl is confirmed by the time-resolved photoluminescence (TRPL) spectra, magnetophotocurrent (MPC) experiment, and electron paramagnetic resonance (EPR) spectra. The effects of side-chain engineering on the optoelectronic properties, packing behaviors, energy losses, charge transport properties, spin lifetimes of triplet polarons, and blend film morphologies are systematically studied. These results show that D18:BT3-4Cl-based OSCs possess the best power conversion efficiency (PCE) of 17.31% due to lower energy losses, less recombination losses, more balanced charge carrier mobilities, longer spin-lattice (T-1) relaxation time, and more favorable morphology. This work enhances the understanding of the structure-property relationship for high-performance triplet acceptors.
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| 36. |
- Zhang, Xin, et al.
(författare)
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High-Performance All-Small-Molecule Organic Solar Cells Enabled by Regio-Isomerization of Noncovalently Conformational Locks
- 2022
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 32:19
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Tidskriftsartikel (refereegranskat)abstract
- The power conversion efficiencies (PCEs) of organic solar cells (OSCs) have surpassed 19% thanks to the innovation of polymer donors and molecular acceptors. However, the batch-to-batch variations in polymer materials are detrimental to the reproducibility of the device performance. In comparison, small-molecule donors (SMDs) possess some unique advantages, such as well-defined molecular weights, easy purification, and excellent batch-to-batch repeatability. Herein, a pair of regioisomeric SMDs (BT-O1 and BT-O2) has been synthesized with alkoxy groups as S center dot center dot center dot O noncovalently conformational locks (NoCLs) at the inner and outer position, respectively. Theoretical and experimental results reveal that the regioisomeric effect has a significant influence on the light-harvest ability, energy levels, molecular geometries, internal reorganization energy, and packing behaviors for the two SMDs. As a result, BT-O2-based binary device shows an impressive PCE of 13.99%, much higher than that of BT-O1 based one (4.07%), due to the better-aligned energy level, more balanced charge transport, less charge recombination, lower energy loss, and more favorable phase separation. Furthermore, the fullerene derivative PC71BM is introduced into BT-O2:H3 as the third component to achieve a notable PCE of 15.34% (certified 14.6%). Overall, this work reveals that NoCLs is a promising strategy to achieve high-performance SMDs for all-small-molecule OSCs.
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| 37. |
- Zhang, Xin, et al.
(författare)
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High-Performance Noncovalently Fused-Ring Electron Acceptors for Organic Solar Cells Enabled by Noncovalent Intramolecular Interactions and End-Group Engineering
- 2021
-
Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 60:22, s. 12475-12481
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Tidskriftsartikel (refereegranskat)abstract
- Noncovalently fused-ring electron acceptors (NFREAs) have attracted much attention in recent years owing to their advantages of simple synthetic routes, high yields and low costs. However, the efficiencies of NFREAs based organic solar cells (OSCs) are still far behind those of fused-ring electron acceptors (FREAs). Herein, a series of NFREAs with S...O noncovalent intramolecular interactions were designed and synthesized with a two-step synthetic route. Upon introducing pi-extended end-groups into the backbones, the electronic properties, charge transport, film morphology, and energy loss were precisely tuned by fine-tuning the degree of multi-fluorination. As a result, a record PCE of 14.53 % in labs and a certified PCE of 13.8 % for NFREAs based devices were obtained. This contribution demonstrated that combining the strategies of noncovalent conformational locks and pi-extended end-group engineering is a simple and effective way to explore high-performance NFREAs.
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| 38. |
- Zhang, Xin, et al.
(författare)
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Side-Chain Engineering for Enhancing the Molecular Rigidity and Photovoltaic Performance of Noncovalently Fused-Ring Electron Acceptors
- 2021
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Ingår i: Angewandte Chemie International Edition. - : WILEY-V C H VERLAG GMBH. - 1433-7851 .- 1521-3773. ; 60:32, s. 17720-17725
-
Tidskriftsartikel (refereegranskat)abstract
- Side-chain engineering is an effective strategy to regulate the solubility and packing behavior of organic materials. Recently, a unique strategy, so-called terminal side-chain (T-SC) engineering, has attracted much attention in the field of organic solar cells (OSCs), but there is a lack of deep understanding of the mechanism. Herein, a new noncovalently fused-ring electron acceptor (NFREA) containing two T-SCs (NoCA-5) was designed and synthesized. Introduction of T-SCs can enhance molecular rigidity and intermolecular pi-pi stacking, which is confirmed by the smaller Stokes shift value, lower reorganization free energy, and shorter pi-pi stacking distance in comparison to NoCA-1. Hence, the NoCA-5-based device exhibits a record power conversion efficiency (PCE) of 14.82 % in labs and a certified PCE of 14.5 %, resulting from a high electron mobility, a short charge-extraction time, a small Urbach energy (E-u), and a favorable phase separation.
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| 39. |
- Zhou, Ruimin, et al.
(författare)
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All-small-molecule organic solar cells with over 14% efficiency by optimizing hierarchical morphologies
- 2019
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- The high efficiency all-small-molecule organic solar cells (OSCs) normally require optimized morphology in their bulk heterojunction active layers. Herein, a small-molecule donor is designed and synthesized, and single-crystal structural analyses reveal its explicit molecular planarity and compact intermolecular packing. A promising narrow bandgap small-molecule with absorption edge of more than 930 nm along with our home-designed small molecule is selected as electron acceptors. To the best of our knowledge, the binary all-small-molecule OSCs achieve the highest efficiency of 14.34% by optimizing their hierarchical morphologies, in which the donor or acceptor rich domains with size up to ca. 70 nm, and the donor crystals of tens of nanometers, together with the donor-acceptor blending, are proved coexisting in the hierarchical large domain. All-small-molecule photovoltaic system shows its promising for high performance OSCs, and our study is likely to lead to insights in relations between bulk heterojunction structure and photovoltaic performance.
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