| 1. |
- Han, Ziqi, et al.
(författare)
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Regulating the miscibility of donors/acceptors to manipulate the morphology and reduce non-radiative recombination energy loss enables efficient organic solar cells
- 2024
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534.
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Tidskriftsartikel (refereegranskat)abstract
- Due to the high exciton binding energy and relatively low charge carrier mobilities of organic photovoltaic materials, it is crucial to optimize the active layer morphology of organic solar cells (OSCs) to well juggle exciton dissociation and charge carrier transport, and inhibit charge carrier recombination for high power conversion efficiencies (PCEs). Herein, we efficiently improve the crystallinity and miscibility of fused ring electron acceptors (FREAs) via lengthening the side chains and developing four FREAs, BTP-nC8, BTP-C8, BTP-C12 and BTP-C20. The dual functions of lengthening the side chains of FREAs make PM6:FREA blend films present the tendency of first improving then deteriorating in crystallinity, phase separation, domain purity and thus charge carrier dynamics, which leads the JSC and FF of PM6:FREA-based OSCs to show the same trend along with the side-chain length of FREAs. More importantly, enhancing the miscibility between PM6 and FREA facilitates the spatial registry to reduce the formation and recombination rate of triplet excitons in the PM6:FREA blend films, thus inhibiting the non-radiative recombination for decreased Delta Enr, and then increasing VOC in OSCs. Among them, PM6:BTP-C8 based OSCs well balance the multiple impacts of lengthening the side chains to achieve the highest PCE of 17.77%. This work demonstrates that it is important to finely control the crystallinity and miscibility of organic photovoltaic materials to achieve high PCEs in OSCs. The miscibility and crystallinity of fused ring electron acceptors is regulated to study the effects on the morphology and energy loss of organic solar cells (OSCs). BTP-C8 based OSCs juggle multiple impacts to gain the best efficiency.
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| 2. |
- Yun, Xiaobo, et al.
(författare)
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Impacts of climate change and reservoir operation on streamflow and flood characteristics in the Lancang-Mekong River Basin
- 2020
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 590
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 Elsevier B.V. The Lancang-Mekong River Basin (LMRB) is one of the most important transboundary river basins in Asia. While climate change perturbs the streamflow and affects flood events, reservoir operation may mitigate or aggravate this impact. Therefore, quantitative assessment of the climate change impact and reservoir effect on the LMRB is a vital prerequisite for future hydropower development and environmental protection. This study aimed to estimate the variation of the streamflow and flood characteristics affected by climate change and reservoir operation within the LMRB. A reservoir module was incorporated into the Variable Infiltration Capacity (VIC) model to simulate the streamflow susceptible to the reservoirs. It was found that the reservoirs had a substantial influence on the streamflow during 2008–2016, when many reservoirs were constructed in the LMRB. The reservoirs across the Lancang River (the upper Mekong River located in China) reduced the annual average streamflow by 5% at Chiang Sean station (northern Thailand) in 2008–2016, whereas their influence became undetectable downstream of Vientiane station (northern Laos). The streamflow changes downstream of Mukdahan station at southern Laos (including the stations in Cambodia and southern Vietnam) were mainly attributed to the local reservoirs and climate change. Compared with the baseline period of 1985–2007, the upstream reservoir operation dramatically affected streamflow at the midstream stations with higher dry season streamflow (+15% to +37%), but lower wet season streamflow was less affected (−2% to −24%) in 2008–2016. Climate change increased the magnitude and frequency of the flood by up to 14% and 45%, respectively, whereas the reservoir operation reduced them by 16% and 36%, respectively. Our findings provide insights into the interaction between climate change and reservoir operation and their integrated effects on the streamflow, informing and supporting water management and hydropower development in the LMRB.
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| 3. |
- Guo, Han, et al.
(författare)
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Transition metal-catalysed molecular n-doping of organic semiconductors
- 2021
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Ingår i: Nature. - London, United Kingdom : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 599:7883, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- Electron doping of organic semiconductors is typically inefficient, but here a precursor molecular dopant is used to deliver higher n-doping efficiency in a much shorter doping time. Chemical doping is a key process for investigating charge transport in organic semiconductors and improving certain (opto)electronic devices(1-9). N(electron)-doping is fundamentally more challenging than p(hole)-doping and typically achieves a very low doping efficiency (eta) of less than 10%(1,10). An efficient molecular n-dopant should simultaneously exhibit a high reducing power and air stability for broad applicability(1,5,6,9,11), which is very challenging. Here we show a general concept of catalysed n-doping of organic semiconductors using air-stable precursor-type molecular dopants. Incorporation of a transition metal (for example, Pt, Au, Pd) as vapour-deposited nanoparticles or solution-processable organometallic complexes (for example, Pd-2(dba)(3)) catalyses the reaction, as assessed by experimental and theoretical evidence, enabling greatly increased eta in a much shorter doping time and high electrical conductivities (above 100 S cm(-1); ref. (12)). This methodology has technological implications for realizing improved semiconductor devices and offers a broad exploration space of ternary systems comprising catalysts, molecular dopants and semiconductors, thus opening new opportunities in n-doping research and applications(12, 13).
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| 4. |
- Li, Yuyang, et al.
(författare)
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Changes in Water Chemistry Associated with Rainstorm Events Increase Carbon Emissions from the Inflowing River Mouth of a Major Drinking Water Reservoir
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:22, s. 16494-16505
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Tidskriftsartikel (refereegranskat)abstract
- Large reservoirs are hotspots for carbon emissions, and the continued input and decomposition of terrestrial dissolved organic matter (DOM) from upstream catchments is an important source of carbon emissions. Rainstorm events can cause a surge in DOM input; however, periodic sampling often fails to fully capture the impact of these discrete rainstorm events on carbon emissions. We conducted a set of frequent observations prior to and following a rainstorm event in a major reservoir Lake Qiandao (China; 580 km(2)) from June to July 2021 to investigate how rainstorms alter water chemistry and CO2 and CH4 emissions. We found that the mean CO2 efflux (FCO2) (13.2 +/- 9.3 mmol m(-)(2) d(-1)) and CH4 efflux (FCH4) (0.12 +/- 0.02 mmol m(-2) d(-1)) in the postrainstorm campaign were significantly higher than those in the prerainstorm campaign (-3.8 +/- 3.0 and +0.06 +/- 0.02 mmol m(-)(2) d(-)(1), respectively). FCO2 and FCH4 increased with increasing nitrogen and phosphorus levels, elevated DOM absorption (a(350)), specific UV absorbance SUVA(254), and terrestrial humic-like fluorescence. Furthermore, FCO2 and FCH4 decreased with increasing chlorophyll-a (Chl-a), dissolved oxygen (DO), and pH. A five-day laboratory anoxic bioincubation experiment further revealed a depletion of terrestrial-DOM concurrent with increased CO2 and CH4 production. We conclude that rainstorms boost the emission of CO2 and CH4 fueled by the surge and decomposition of fresh terrestrially derived biolabile DOM in this and likely many other reservoir's major inflowing river mouths.
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| 5. |
- 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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| 6. |
- Wang, Jinling, et al.
(författare)
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Urbanization in developing countries overrides catchment productivity in fueling inland water CO2 emissions
- 2022
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 29:1, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- We compiled a nationwide dataset of carbon dioxide (CO2) efflux from 1405 measurements, and found that lakes, reservoirs, and rivers emit a total of 61.9 ± 55.3 TgC as CO2 each year, corresponding to 6.3% of the annual total national CO2 emission in 2020. Our analysis showed that the presence of anthropogenic disturbances in catchments strongly influences the emission of CO2 from these waters in the non-pristine areas, masking the catchment productivity effect on the emission of CO2. Our results highlight the need for adjusting climate change models for taking into account anthropogenic effects on CO2 emissions from inland waters.
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| 7. |
- Zhou, Lei, et al.
(författare)
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Eutrophication alters bacterial co-occurrence networks and increases the importance of chromophoric dissolved organic matter composition
- 2021
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:6, s. 2319-2332
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Tidskriftsartikel (refereegranskat)abstract
- Eutrophication affects bacterial communities by fueling them with nutrients and carbon sources. While the influence of physicochemical conditions on bacterial communities is well studied, little is known about how dissolved organic matter (DOM) quality affects bacterial interspecific interactions and community composition with increasing eutrophication. Here, we examined the relative importance of physicochemical conditions and chromophoric DOM (CDOM) composition for bacterial community variation across trophic gradients using 109 samples data collected in 33 lakes of the Yangtze-Huaihe River basin. We found a notable increase of bacterial abundance, elevated modularity of co-occurrence networks, and decreased habitat niche breadths from mesotrophic sites to hyper-eutrophic sites, suggesting changes in co-occurrence patterns with eutrophication. Variation partitioning revealed that the proportion purely explained by CDOM composition was higher at the moderate- and hyper-eutrophic sites than at the mesotrophic sites. Moreover, the module structures of the networks correlated significantly with CDOM composition at the eutrophic sites but not at the mesotrophic sites. The significant negative correlation between community-level habitat niche breadths and the intensities of the protein-like components at the moderate- and hyper-eutrophic sites indicates a strong association between biolabile protein-like compounds and habitat specialists in nutrient and substrate enriched lake systems. Our results suggest that consideration of DOM composition can strengthen the identification of links between environmental factors and bacterial community composition and interspecific interactions, especially under resource-rich conditions.
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| 8. |
- Zhou, Lei, et al.
(författare)
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Resource aromaticity affects bacterial community successions in response to different sources of dissolved organic matter
- 2021
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Microbe-mediated transformation of dissolved organic matter (DOM) contributes substantially to the carbon dynamics and energy flow of aquatic ecosystems; yet, the temporal dynamics of bacterial communities in response to diverse DOM sources are scarcely known. Here, we supplied four distinct sources of DOM (algae-derived, macrophyte-derived, sewage-derived, and soil-derived) to the same bacterial community to track the effects of these DOM sources on the carbon processing and successional dynamics of bacterial communities. Although by the end of the incubation the proportion of bio-degraded DOM was significantly lower in the soil-derived DOM treatment than for the other sources, rapid initial metabolism of protein-like and aliphatic compounds and increasing aromaticity and humification degree of DOM during the incubation period were observed for all sources. The role of stochastic processes in governing the community assembly decreased substantially from 61.4% on the first day to 16.7% at the end of the incubation. Moreover, stronger deterministic selection and lower temporal turnover rate were observed for the soil-derived than the other DOM sources, indicating stronger environmental filtering by the more aromatic DOM. Significant correlations were also observed between the humification index (HIX) of DOM and bacterial community diversities, co-occurrence patterns, habitat niche breadths, and the contribution of deterministic ecological processes. In addition, we demonstrated that taxa with different abundance patterns all play crucial but different roles in the response to DOM variation. Our results indicate the importance of DOM aromaticity as a predictor of the outcome of different DOM sources on bacterial community dynamics.
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| 9. |
- Zhou, Yongqiang, et al.
(författare)
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How hydrology and anthropogenic activity influence the molecular composition and export of dissolved organic matter : Observations along a large river continuum
- 2021
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:5, s. 1730-1742
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Tidskriftsartikel (refereegranskat)abstract
- Large rivers are the main arteries for transportation of carbon to the ocean; yet, how hydrology and anthropogenic disturbances may change the composition and export of dissolved organic matter along large river continuums is largely unknown. The Yangtze River has a watershed area of 1.80 x 10(6) km(2). It originates from the Qinghai-Tibet Plateau and flows 6300 km eastward through the center of China. We collected samples (n = 271) along the river continuum and analyzed weekly samples at the most downstream situated gauging station in 2017-2018 and gathered long-term (2006-2018) water quality data. We found higher gross domestic product, population density, and urban and agricultural land use downstream than upstream of the Three Gorges Dam, coinciding with higher dissolved organic carbon (DOC), UV absorption (a(254)), specific ultraviolet absorbance (SUVA(254)), parallel factor analysis-derived C1-C5, aliphatic compounds, and lower a(250):a(365) and spectral slope (S275-295). Chemical oxygen demand, humic-like C1-C2 and C6, and protein-like C4 and C7 increased, while dissolved oxygen and ammonium decreased with increasing discharge at most of the sites studied, including the intensively monitored downstream site. The annual DOC fluxes were ca. 1.5-1.8 Tg yr(-1), and 12-18% was biodegradable in a 28-d bio-incubation. Our results highlight that urbanization and stormwater periods enhanced the export of both terrestrial organic-rich substances and household effluents from nearshore residential areas. Our study emphasizes the continued need to protect the Yangtze River watershed as increased organic carbon loading or altered composition and bio-lability may change the ecosystem function and carbon cycling.
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| 10. |
- Zhou, Yongqiang, et al.
(författare)
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Key factors driving dissolved organic matter composition and bioavailability in lakes situated along the Eastern Route of the South-to-North Water Diversion Project, China
- 2023
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Ingår i: Water Research. - : Elsevier. - 0043-1354 .- 1879-2448. ; 233
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Tidskriftsartikel (refereegranskat)abstract
- The Eastern Route of the South-to-North Water Diversion Project (SNWDP-ER) is a large scale multi-decade infrastructure project aiming to divert substantial amounts of water (approximate to 45 billion m3 yr-1) to alleviate water shortage in comparatively arid regions of northern China. The project has ramifications for hydrological con-nectivity and biogeochemical cycling of dissolved organic matter (DOM) in regional lakes affected by the project. We carried out an extensive field sampling campaign along the SNWDP-ER in different hydrological seasons of 2018 and monthly observations in Lake Hongze and Lake Luoma from April 2018 to June 2021. We found the lakes connecting to the SNWDP-ER had higher mean DOC, specific UV absorbance, higher ratio of humic-like to protein-like fluorophores (Humic : Protein), and shallower spectral slope (S275-295) in the wet season compared to the wet-to-dry transition, and dry seasons. The southern lakes and Yangtze River had lower DOC concen-tration, bioavailable DOC (BDOC), and higher DOM aromaticity compared to the northern two downstream lakes. Ultrahigh-resolution mass spectrometry (FT-ICR MS) revealed higher relative abundance of CHO-containing and aromatic compounds in the Yangtze River and the southern three upstream lakes compared to the northern two lakes. The data from Lake Hongze and Lake Luoma, studied in different hydrological seasons, suggest that water delivery had high consistency in DOM composition and BDOC over the season. We conclude that positioning along the watercourse and seasonally variable hydrological conditions play an important role in influencing the DOM composition and bioavailability of key lakes connecting to the SNWDP-ER. Our results indicated that the water diversion project delivers water with low DOC concentration and higher aromaticity and thus is of higher quality since it has higher DOM removal potential during drinking water treatment.
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