| 1. |
- Chen, Haiyang, et al.
(författare)
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A guest-assisted molecular-organization approach for >17% efficiency organic solar cells using environmentally friendly solvents
- 2021
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Ingår i: Nature Energy. - : NATURE PORTFOLIO. - 2058-7546. ; 6:11, s. 1045-1053
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Tidskriftsartikel (refereegranskat)abstract
- The power conversion efficiencies (PCEs) of laboratory-sized organic solar cells (OSCs), usually processed from low-boiling-point and toxic solvents, have reached high values of over 18%. However, there is usually a notable drop of the PCEs when green solvents are used, limiting practical development of OSCs. Herein, we obtain certificated PCEs over 17% in OSCs processed from a green solvent paraxylene (PX) by a guest-assisted assembly strategy, where a third component (guest) is employed to manipulate the molecular interaction of the binary blend. In addition, the high-boiling-point green solvent PX also enables us to deposit a uniform large-area module (36 cm(2)) with a high efficiency of over 14%. The strong molecular interaction between the host and guest molecules also enhances the operational stability of the devices. Our guest-assisted assembly strategy provides a unique approach to develop large-area and high-efficiency OSCs processed from green solvents, paving the way for industrial development of OSCs. Organic solar cells processed from green solvents are easier to implement in manufacturing yet their efficiency is low. Chen et al. devise a guest molecule to improve the molecular packing, enabling devices with over 17% efficiency.
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| 2. |
- Chen, Xian-Kai, et al.
(författare)
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A unified description of non-radiative voltage losses in organic solar cells
- 2021
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Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 6:8, s. 799-806
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Tidskriftsartikel (refereegranskat)abstract
- Organic solar cells based on non-fullerene acceptors have enabled high efficiencies yet their charge dynamics and its impact on the photovoltaic parameters are not fully understood. Now, Chen et al. provide a general description of non-radiative voltage losses in both fullerene and non-fullerene solar cells. Recent advances in organic solar cells based on non-fullerene acceptors (NFAs) come with reduced non-radiative voltage losses (Delta V-nr). Here we show that, in contrast to the energy-gap-law dependence observed in conventional donor:fullerene blends, the Delta V-nr values in state-of-the-art donor:NFA organic solar cells show no correlation with the energies of charge-transfer electronic states at donor:acceptor interfaces. By combining temperature-dependent electroluminescence experiments and dynamic vibronic simulations, we provide a unified description of Delta V-nr for both fullerene- and NFA-based devices. We highlight the critical role that the thermal population of local exciton states plays in low-Delta V-nr systems. An important finding is that the photoluminescence yield of the pristine materials defines the lower limit of Delta V-nr. We also demonstrate that the reduction in Delta V-nr (for example, <0.2 V) can be obtained without sacrificing charge generation efficiency. Our work suggests designing donor and acceptor materials with high luminescence efficiency and complementary optical absorption bands extending into the near-infrared region.
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| 3. |
- Cherp, Aleh, et al.
(författare)
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National growth dynamics of wind and solar power compared to the growth required for global climate targets
- 2021
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Ingår i: Nature Energy. - : Springer Science and Business Media LLC. - 2058-7546. ; 6:7, s. 742-754
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Tidskriftsartikel (refereegranskat)abstract
- Climate mitigation scenarios envision considerable growth of wind and solar power, but scholars disagree on how this growth compares with historical trends. Here we fit growth models to wind and solar trajectories to identify countries in which growth has already stabilized after the initial acceleration. National growth has followed S-curves to reach maximum annual rates of 0.8% (interquartile range of 0.6–1.1%) of the total electricity supply for onshore wind and 0.6% (0.4–0.9%) for solar. In comparison, one-half of 1.5 °C-compatible scenarios envision global growth of wind power above 1.3% and of solar power above 1.4%, while one-quarter of these scenarios envision global growth of solar above 3.3% per year. Replicating or exceeding the fastest national growth globally may be challenging because, so far, countries that introduced wind and solar power later have not achieved higher maximum growth rates, despite their generally speedier progression through the technology adoption cycle.
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| 4. |
- Guo, Renjun, et al.
(författare)
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Degradation mechanisms of perovskite solar cells under vacuum and one atmosphere of nitrogen
- 2021
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Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 6:10, s. 977-
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Tidskriftsartikel (refereegranskat)abstract
- Extensive studies have focused on improving the operational stability of perovskite solar cells, but few have surveyed the fundamental degradation mechanisms. One aspect overlooked in earlier works is the effect of the atmosphere on device performance during operation. Here we investigate the degradation mechanisms of perovskite solar cells operated under vacuum and under a nitrogen atmosphere using synchrotron radiation-based operando grazing-incidence X-ray scattering methods. Unlike the observations described in previous reports, we find that light-induced phase segregation, lattice shrinkage and morphology deformation occur under vacuum. Under nitrogen, only lattice shrinkage appears during the operation of solar cells, resulting in better device stability. The different behaviour under nitrogen is attributed to a larger energy barrier for lattice distortion and phase segregation. Finally, we find that the migration of excessive PbI2 to the interface between the perovskite and the hole transport layer degrades the performance of devices under vacuum or under nitrogen. Understanding degradation mechanisms in perovskite solar cells is key to their development. Now, Guo et al. show a greater degradation of the perovskite structure and morphology for devices operated under vacuum than under nitrogen.
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| 5. |
- Li, Chao, et al.
(författare)
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Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells
- 2021
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Ingår i: Nature Energy. - : NATURE RESEARCH. - 2058-7546.
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Tidskriftsartikel (refereegranskat)abstract
- Molecular design of acceptor and donor molecules has enabled major progress in organic photovoltaics. Li et al. show that branched alkyl chains in non-fullerene acceptors allow favourable morphology in the active layer, enabling a certified device efficiency of 17.9%. Molecular design of non-fullerene acceptors is of vital importance for high-efficiency organic solar cells. The branched alkyl chain modification is often regarded as a counter-intuitive approach, as it may introduce an undesirable steric hindrance that reduces charge transport in non-fullerene acceptors. Here we show the design and synthesis of a highly efficient non-fullerene acceptor family by substituting the beta position of the thiophene unit on a Y6-based dithienothiophen[3,2-b]-pyrrolobenzothiadiazole core with branched alkyl chains. It was found that such a modification to a different alkyl chain length could completely change the molecular packing behaviour of non-fullerene acceptors, leading to improved structural order and charge transport in thin films. An unprecedented efficiency of 18.32% (certified value of 17.9%) with a fill factor of 81.5% is achieved for single-junction organic solar cells. This work reveals the importance of the branched alkyl chain topology in tuning the molecular packing and blend morphology, which leads to improved organic photovoltaic performance.
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| 6. |
- Nielsen, Kristian S., et al.
(författare)
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The role of high-socioeconomic-status people in locking in or rapidly reducing energy-driven greenhouse gas emissions
- 2021
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Ingår i: Nature Energy. - : Springer Science and Business Media LLC. - 2058-7546. ; 6:11, s. 1011-1016
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Tidskriftsartikel (refereegranskat)abstract
- People with high socioeconomic status disproportionally affect energy-driven greenhouse gas emissions directly through their consumption and indirectly through their financial and social resources. However, few climate change mitigation initiatives have targeted this population segment, and the potential of such initiatives remains insufficiently researched. In this Perspective, we analyse key characteristics of high-socioeconomic-status people and explore five roles through which they have a disproportionate impact on energy-driven greenhouse gas emissions and potentially on climate change mitigation, namely as consumers, investors, role models, organizational participants and citizens. We examine what is known about their disproportionate impact via consumption and explore their potential influence on greenhouse gas emissions through all five roles. We suggest that future research should focus on strategies to reduce greenhouse gas emissions by high-socioeconomic-status people and to align their investments, organizational choices and actions as social and political change agents with climate change mitigation goals.
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| 7. |
- Taalbi, Josef, et al.
(författare)
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The role of energy infrastructure in shaping early adoption of electric and gasoline cars
- 2021
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Ingår i: Nature Energy. - : Springer Science and Business Media LLC. - 2058-7546. ; 6:10, s. 970-976
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Tidskriftsartikel (refereegranskat)abstract
- Electric vehicles have a potential to lower greenhouse gas emissions but still face challenges. This study asks what can be learned from the US automobile history. In 1900, there were three equal contenders in the US automotive industry: gasoline, electric and steam cars. Only a decade later, the gasoline car had achieved a crushing dominance. This dominance is often attributed to techno-economic factors, such as an innate inferiority of electric cars. Meanwhile, the role of the infrastructures is not well understood. This study presents evidence on the mechanisms behind the rise of gasoline vehicles, using a database of more than 36,000 passenger car models. We estimated econometric models to explain the technology choice of car producers, which show that the slow expansion of electricity infrastructure had a key impact. We estimate that a 15 or 20 year earlier diffusion of electricity grids would have tipped the balance in favour of electric vehicles, most notably in metropolitan areas. In the context of the current climate crisis, the results support the notion that large-scale investment in infrastructure is critical to achieve sustainable socio-technological transitions.
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