| 1. |
- Duan, Chunhui, et al.
(författare)
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Improving Performance of All-Polymer Solar Cells Through Backbone Engineering of Both Donors and Acceptors
- 2018
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 2:12
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Tidskriftsartikel (refereegranskat)abstract
- All-polymer solar cells (APSCs), composed of semiconducting donor and acceptor polymers, have attracted considerable attention due to their unique advantages compared to polymer-fullerene-based devices in terms of enhanced light absorption and morphological stability. To improve the performance of APSCs, the morphology of the active layer must be optimized. By employing a random copolymerization strategy to control the regularity of the backbone of the donor polymers (PTAZ-TPDx) and acceptor polymers (PNDI-Tx) the morphology can be systematically optimized by tuning the polymer packing and crystallinity. To minimize effects of molecular weight, both donor and acceptor polymers have number-average molecular weights in narrow ranges. Experimental and coarse-grained modeling results disclose that systematic backbone engineering greatly affects the polymer crystallinity and ultimately the phase separation and morphology of the all-polymer blends. Decreasing the backbone regularity of either the donor or the acceptor polymer reduces the local crystallinity of the individual phase in blend films, affording reduced short-circuit current densities and fill factors. This two-dimensional crystallinity optimization strategy locates a PCE maximum at highest crystallinity for both donor and acceptor polymers. Overall, this study demonstrates that proper control of both donor and acceptor polymer crystallinity simultaneously is essential to optimize APSC performance.
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| 2. |
- Feng, Guitao, et al.
(författare)
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“Double-Cable” Conjugated Polymers with Linear Backbone toward High Quantum Efficiencies in Single-Component Polymer Solar Cells
- 2017
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 139:51, s. 18647-18656
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Tidskriftsartikel (refereegranskat)abstract
- A series of "double-cable" conjugated polymers were developed for application in efficient single-component polymer solar cells, in which high quantum efficiencies could be achieved due to the optimized nanophase separation between donor and acceptor parts. The new double-cable polymers contain electron-donating poly(benzodithiophene) (BDT) as linear conjugated backbone for hole transport and pendant electron-deficient perylene bisimide (PBI) units for electron transport, connected via a dodecyl linker. Sulfur and fluorine substituents were introduced to tune the energy levels and crystallinity of the conjugated polymers. The double-cable polymers adopt a "face-on" orientation in which the conjugated BDT backbone and the pendant PBI units have a preferential pi-pi stacking direction perpendicular to the substrate, favorable for interchain charge transport normal to the plane. The linear conjugated backbone acts as a scaffold for the crystallization of the PBI groups, to provide a double-cable nanophase separation of donor and acceptor phases. The optimized nanophase separation enables efficient exciton dissociation as well as charge transport as evidenced from the high-up to 80%-internal quantum efficiency for photon-to-electron conversion. In single-component organic solar cells, the double-cable polymers provide power conversion efficiency up to 4.18%. This is one of the highest performances in single-component organic solar cells. The nanophase-separated design can likely be used to achieve high-performance single-component organic solar cells.
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| 3. |
- Hansson, Rickard, 1987-
(författare)
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Materials and Device Engineering for Efficient and Stable Polymer Solar Cells
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Polymer solar cells form a promising technology for converting sunlight into electricity, and have reached record efficiencies over 10% and lifetimes of several years. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor materials in the active layer. To achieve longer lifetimes, degradation processes in the materials have to be understood. In this thesis, a set of complementary spectroscopy and microscopy techniques, among which soft X-ray techniques have been used to determine the morphology of polymer:fullerene based active layers. We have found that the morphology of TQ1:PC70BM films is strongly influenced by the processing solvent and the use of solvent additives. We have also found, by using soft X-ray techniques, that not only the light-absorbing polymer TQ1, but also the fullerene is susceptible to photo-degradation in air. Moreover, the fullerene degradation is accelerated in the presence of the polymer. Additionally, this thesis addresses the role of the interfacial layers for device performance and stability. The commonly used hole transport material PEDOT:PSS has the advantage of being solution processable at room temperature, but this layer is also known to contribute to the device degradation. We have found that low-temperature processed NiOx is a promising alternative to PEDOT:PSS, leading to improved device performance. Even for encapsulated polymer solar cells, some photo-induced degradation of the electrical performance is observed and is found to depend on the nature of the hole transport material. We found a better initial stability for solar cells with MoO3 hole transport layers than with PEDOT:PSS. In the pursuit of understanding the initial decrease in electrical performance of PEDOT:PSS-based devices, simulations were performed, from which a number of degradation sources could be excluded.
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| 4. |
- Janssen, Annette B. G., et al.
(författare)
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Exploring, exploiting and evolving diversity of aquatic ecosystem models : a community perspective
- 2015
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Ingår i: Aquatic Ecology. - : Springer Science and Business Media LLC. - 1386-2588 .- 1573-5125. ; 49:4, s. 513-548
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Tidskriftsartikel (refereegranskat)abstract
- Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.
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| 5. |
- Khikhlovskyi, Vsevolod, et al.
(författare)
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3D-Morphology Reconstruction of Nanoscale Phase-Separation in Polymer Memory Blends
- 2015
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Ingår i: Journal of Polymer Science Part B. - : John Wiley & Sons. - 0887-6266 .- 1099-0488. ; 53:17, s. 1231-1237
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Tidskriftsartikel (refereegranskat)abstract
- In many organic electronic devices functionality is achieved by blending two or more materials, typically polymers or molecules, with distinctly different optical or electrical properties in a single film. The local scale morphology of such blends is vital for the device performance. Here, a simple approach to study the full 3D morphology of phase-separated blends, taking advantage of the possibility to selectively dissolve the different components is introduced. This method is applied in combination with AFM to investigate a blend of a semiconducting and ferroelectric polymer typically used as active layer in organic ferroelectric resistive switches. It is found that the blend consists of a ferroelectric matrix with three types of embedded semiconductor domains and a thin wetting layer at the bottom electrode. Statistical analysis of the obtained images excludes the presence of a fourth type of domains. The criteria for the applicability of the presented technique are discussed. (c) 2015 Wiley Periodicals, Inc.
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| 6. |
- Khikhlovskyi, Vsevolod, et al.
(författare)
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Data retention in organic ferroelectric resistive switches
- 2016
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Ingår i: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 31, s. 56-62
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Tidskriftsartikel (refereegranskat)abstract
- Solution-processed organic ferroelectric resistive switches could become the long-missing non-volatile memory elements in organic electronic devices. To this end, data retention in these devices should be characterized, understood and controlled. First, it is shown that the measurement protocol can strongly affect the apparent retention time and a suitable protocol is identified. Second, it is shown by experimental and theoretical methods that partial depolarization of the ferroelectric is the major mechanism responsible for imperfect data retention. This depolarization occurs in close vicinity to the semiconductor-ferroelectric interface, is driven by energy minimization and is inherently present in this type of phase-separated polymer blends. Third, a direct relation between data retention and the charge injection barrier height of the resistive switch is demonstrated experimentally and numerically. Tuning the injection barrier height allows to improve retention by many orders of magnitude in time, albeit at the cost of a reduced on/off ratio. (c) 2016 Elsevier B.V. All rights reserved.
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| 7. |
- Lee, Jiyoul, et al.
(författare)
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Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6:24407
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses. The resulting 2-bit data storage per memory element doubles the storage density of the organic ferroelectric resistive memory diode without increasing its technological complexity, thus reducing the cost per bit.
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| 8. |
- Li, Zhaojun, 1989, et al.
(författare)
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9.0% power conversion efficiency from ternary all-polymer solar cells
- 2017
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Ingår i: Energy and Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 10:10, s. 2212-2221
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Tidskriftsartikel (refereegranskat)abstract
- Integration of a third component into a single-junction polymer solar cell (PSC) is regarded as an attractive strategy to enhance the performance of PSCs. Although binary all-polymer solar cells (all-PSCs) have recently emerged with compelling power conversion efficiencies (PCEs), the PCEs of ternary all-PSCs still lag behind those of the state-of-the-art binary all-PSCs, and the advantages of ternary systems are not fully exploited. In this work, we realize high-performance ternary all-PSCs with record-breaking PCEs of 9% and high fill factors (FF) of over 0.7 for both conventional and inverted devices. The improved photovoltaic performance benefits from the synergistic effects of extended absorption, more efficient charge generation, optimal polymer orientations and suppressed recombination losses compared to the binary all-PSCs, as evidenced by a set of experimental techniques. The results provide new insights for developing high-performance ternary all-PSCs by choosing appropriate donor and acceptor polymers to overcome limitations in absorption, by affording good miscibility, and by benefiting from charge and energy transfer mechanisms for efficient charge generation.
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| 9. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-Performance and Stable All-Polymer Solar Cells Using Donor and Acceptor Polymers with Complementary Absorption
- 2017
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 7:14
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Tidskriftsartikel (refereegranskat)abstract
- To explore the advantages of emerging all-polymer solar cells (all-PSCs), growing efforts have been devoted to developing matched donor and acceptor polymers to outperform fullerene-based PSCs. In this work, a detailed characterization and comparison of all-PSCs using a set of donor and acceptor polymers with both conventional and inverted device structures is performed. A simple method to quantify the actual composition and light harvesting contributions from the individual donor and acceptor is described. Detailed study on the exciton dissociation and charge recombination is carried out by a set of measurements to understand the photocurrent loss. It is unraveled that fine-tuned crystallinity of the acceptor, matched donor and acceptor with complementary absorption and desired energy levels, and device architecture engineering can synergistically boost the performance of all-PSCs. As expected, the PBDTTS-FTAZ:PNDI-T10 all-PSC attains a high and stable power conversion efficiency of 6.9% without obvious efficiency decay in 60 d. This work demonstrates that PNDI-T10 can be a potential alternative acceptor polymer to the widely used acceptor N2200 for high-performance and stable all-PSCs.
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| 10. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-photovoltage all-polymer solar cells based on a diketopyrrolopyrrole-isoindigo acceptor polymer
- 2017
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 5:23, s. 11693-11700
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we synthesized and characterized two new n-type polymers PTDPP-PyDPP and PIID-PyDPP. The former polymer is composed of pyridine-flanked diketopyrrolopyrrole (PyDPP) and thiophene-flanked diketopyrrolopyrrole (TDPP). The latter polymer consists of PyDPP and isoindigo (IID). PIID-PyDPP exhibits a much higher absorption coefficient compared to the widely used naphthalene diimide (NDI)-based acceptor polymers, and its high-lying LUMO level affords it to achieve a high open-circuit voltage (Voc). As a result, an all-polymer solar cell (all-PSC) fabricated from a high band gap polymer PBDTTS-FTAZ as the donor and PIID-PyDPP as the acceptor attained a high Voc of 1.07 V with a power conversion efficiency (PCE) of 4.2%. So far, it has been one of the highest PCEs recorded from all-PSCs using diketopyrrolopyrrole (DPP)-based acceptors. Gratifyingly, no obvious PCE decay was observed in two weeks, unraveling good stability of the all-PSC. This work demonstrates that the electron-withdrawing PyDPP unit can be a promising building block for new acceptor polymers in all-PSCs.
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| 11. |
- Meng, Xiao, et al.
(författare)
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Ferroelectric Switching and Electrochemistry of Pyrrole Substituted Trialkylbenzene-1,3,5-Tricarboxamides
- 2017
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Ingår i: Journal of Polymer Science Part B. - : WILEY. - 0887-6266 .- 1099-0488. ; 55:8, s. 673-683
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Tidskriftsartikel (refereegranskat)abstract
- We explore a new approach to organic ferroelectric diodes using a benzene-tricarboxamide (BTA) core connected with C10 alkyl chains to pyrrole groups, which can be polymerized to provide a semiconducting ferroelectric material. The compound possesses a columnar hexagonal liquid crystalline (LC) phase and exhibits ferroelectric switching. At low switching frequencies, an additional process occurs, which leads to a high hysteretic charge density of up to similar to 1000 mC/m(2). Based on its slow rate, the formation of gas bubbles, and the emergence of characteristic polypyrrole absorption bands in the UV-Vis-NIR, the additional process is identified as the oxidative polymerization of pyrrole groups, enabled by the presence of amide groups. Polymerization of the pyrrole groups, which is essential to obtain semiconductivity, is limited to thin layers at the electrodes, amounting to similar to 17 nm after cycling for 21 h. (C) 2017 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc.
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| 12. |
- van Breemen, Albert, et al.
(författare)
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Surface Directed Phase Separation of Semiconductor Ferroelectric Polymer Blends and their Use in Non-Volatile Memories
- 2015
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 25:2, s. 278-286
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Tidskriftsartikel (refereegranskat)abstract
- The polymer phase separation of P(VDF-TrFE):F8BT blends is studied in detail. Its morphology is key to the operation and performance of memory diodes. In this study, it is demonstrated that it is possible to direct the semiconducting domains of a phase-separating mixture of P(VDF-TrFE) and F8BT in a thin film into a highly ordered 2D lattice by means of surface directed phase separation. Numerical simulation of the surface-controlled de-mixing process provides insight in the ability of the substrate pattern to direct the phase separation, and hence the regularity of the domain pattern in the final dry blend layer. By optimizing the ratio of the blend components, the number of electrically active semiconductor domains is maximized. Pattern replication on a cm-scale is achieved, and improved functional device performance is demonstrated in the form of a 10-fold increase of the ON-current and a sixfold increase in current modulation. This approach therefore provides a simple and scalable means to higher density integration, the ultimate target being a single semiconducting domain per memory cell.
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| 13. |
- van Reenen, Stephan, et al.
(författare)
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Fundamental Tradeoff between Emission Intensity and Efficiency in Light-Emitting Electrochemical Cells
- 2015
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Ingår i: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 25:20, s. 3066-3073
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Tidskriftsartikel (refereegranskat)abstract
- The characteristic doping process in polymer light-emitting electrochemical cells (LECs) causes a tradeoff between luminescence intensity and efficiency. Experiments and numerical modeling on thin film polymer LECs show that, on the one hand, carrier injection and transport benefit from electrochemical doping, leading to increased electron-hole recombination. On the other hand, the radiative recombination efficiency is reduced by exciton quenching by polarons involved in the doping. Consequently, the quasi-steady-state luminescent efficiency decreases with increasing ion concentration. The transient of the luminescent efficiency shows a characteristic roll-off while the current continuously increases, attributed to ongoing electrochemical doping and the associated exciton quenching. Both effects can be modeled by exciton polaron-quenching via diffusion-assisted Forster resonance energy transfer. These results indicate that the tradeoff between efficiency and intensity is fundamental, suggesting that the application realm of future LECs should be sought in high-brightness, low-production cost devices, rather than in high-efficiency devices.
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| 14. |
- Verheul, Marije K., et al.
(författare)
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Triple positivity for anti–citrullinated protein autoantibodies, rheumatoid factor, and anti–carbamylated protein antibodies conferring high specificity for rheumatoid arthritis : implications for very early identification of at‐risk individuals
- 2018
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Ingår i: Arthritis & Rheumatology. - Hoboken : John Wiley & Sons. - 2326-5191 .- 2326-5205. ; 70:11, s. 1721-1731
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: In rheumatoid arthritis(RA), the autoantibodies anti-citrullinated protein antibodies(ACPA) and rheumatoid factor(RF) are commonly used to aid RA diagnosis. Although these autoantibodies are mainly found in RA, their specificity is not optimal. It is therefore difficult to identify RA patients, especially in very early disease, based on the presence of ACPA and RF alone. Also, anti-carbamylated protein(anti-CarP) antibodies have diagnostic and prognostic value as the presence of anti-CarP antibodies associates with joint damage in RA patients and with future RA development in arthralgia patients. Therefore, we aimed to investigate the value of combined antibody testing in relation to prediction and diagnosis of (early) RA.METHODS: A literature search resulted in twelve studies, consisting of RA patients, pre-RA individuals, disease controls, healthy first-degree relatives of RA patients or healthy controls, in which data on RF, ACPA and anti-CarP antibody-status was available. Random effects meta-analyses were carried out for several antibody combinations.RESULTS: The individual antibodies are highly prevalent in RA(34%-80%) compared to the control groups, but are also present in non-RA controls(0%-23%). To classify most people correctly as RA or non-RA, the combination of ACPA and/or RF often performs well(specificity:65-100, sensitivity:59-88). However, triple positivity for ACPA, RF and anti-CarP antibodies results in a higher specificity(98-100) (accompanied by a lower sensitivity(11-39)).CONCLUSIONS: As the rheumatology field is moving towards very early identification of RA and possible screening for individuals at maximum risk in populations with a low pre-test probability, triple positivity provides interesting information on individuals at risk to develop RA.
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| 15. |
- Xu, Xiaofeng, 1984, et al.
(författare)
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8.0% Efficient All-Polymer Solar Cells with High Photovoltage of 1.1 V and Internal Quantum Efficiency near Unity
- 2018
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- In very recent years, growing efforts have been devoted to the development of all-polymer solar cells (all-PSCs). One of the advantages of all-PSCs over the fullerene-based PSCs is the versatile design of both donor and acceptor polymers which allows the optimization of energy levels to maximize the open-circuit voltage (Voc). However, there is no successful example of all-PSCs with both high Voc over 1 V and high power conversion efficiency (PCE) up to 8% reported so far. In this work, a combination of a donor polymer poly[4,8-bis(5-(2-octylthio)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-(5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione)-1,3-diyl] (PBDTS-TPD) with a low-lying highest occupied molecular orbital level and an acceptor polymer poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-thiophene-2,5-diyl] (PNDI-T) with a high-lying lowest unoccupied molecular orbital level is used, realizing high-performance all-PSCs with simultaneously high Voc of 1.1 V and high PCE of 8.0%, and surpassing the performance of the corresponding PC71BM-based PSCs. The PBDTS-TPD:PNDI-T all-PSCs achieve a maximum internal quantum efficiency of 95% at 450 nm, which reveals that almost all the absorbed photons can be converted into free charges and collected by electrodes. This work demonstrates the advantages of all-PSCs by incorporating proper donor and acceptor polymers to boost both Voc and PCEs.
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