Nowadays, organic solar cells (OSCs) with Y6 and its derivatives as electron acceptors provide the highest efficiencies among the studied binary OSCs. To further improve the performances of OSCs, the ...fabrication of ternary OSCs (TOSCs) is a convenient strategy. Essentially, morphology control and the trade-off between voltage and photocurrent are the main critical issues in TOSCs. Herein, we address these problems by constructing TOSCs where an alloy-like composite is formed between Y6 and a newly designed derivative, BTP-M. Employing an electron-pushing methyl substituent as a replacement for the electron-withdrawing F atoms on Y6, BTP-M shows higher energy levels and lower crystallinity than Y6. As a result, the obtained Y6:BTP-M alloy can simultaneously optimize energy levels to reduce energy loss as well as the morphologies of the active layers to favor photocurrent generation, leading to an enhanced open-circuit voltage (
V
oc
) of 0.875 V together with a larger short-circuit current density (
J
sc
) of 26.56 mA cm
−2
for TOSCs based on the polymer donor PM6 and Y6:BTP-M acceptor alloy. Consequently, a best efficiency of 17.03% is achieved for the corresponding TOSCs, which is among the best values for single-junction OSCs. In addition, our TOSCs also exhibit good thickness tolerance, and can reach 14.23% efficiency even though the active layer is as thick as 300 nm.
An alloy-like model based on Y6 and its derivative BTP-M is constructed to fabricate ternary organic solar cells, leading to a best efficiency of 17.03%.
Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). The surface properties of the substrates on which crystalline perovskite thin films form are ...expected to affect greatly the crystallization and, thus, the resulting morphology. However, this topic is seldom examined in PSC. Here we developed a facile but efficient method of modifying the ZnO-coated substrates with 3-aminopropanioc acid (C3-SAM) to direct the crystalline evolution and achieve the optimal morphology of CH3NH3PbI3 perovskite film. With incorporation of the C3-SAM, highly crystalline CH3NH3PbI3 films were formed with reduced pin-holes and trap states density. In addition, the work function of the cathode was better aligned with the conduction band minimum of perovskite for efficient charge extraction and electronic coupling. As a result, the PSC performance remarkably increased from 9.81(±0.99)% (best 11.96%) to 14.25(±0.61)% (best 15.67%). We stress the importance of morphology control through substrate surface modification to obtain the optimal morphology and device performance of PSC, which should generate an impact on developing highly efficient PSC and future commercialization.
Organic single‐crystalline heterojunctions are composed of different single crystals interfaced together. The intrinsic highly ordered heterostructure in these multicomponent solids holds the ...capacity for multifunctions, as well as superior charge‐transporting properties, promising high‐performance electronic applications such as ambipolar transistors and solar cells. However, this kind of heterojunction is not easily available and the preparation methods need to be developed. Recent advances in the efficient strategies that have emerged in yielding high‐quality single‐crystalline heterojunctions are highlighted here. The advantages and limitations of each strategy are also discussed. The obtained single‐crystalline heterojunctions have started to exhibit rich physical properties, including metallic conduction, photovoltaic effects, and so on. Further structural optimization of the heterojunctions to accommodate the electronic device configuration is necessary to significantly advance this research direction.
The recent progress of organic single‐crystalline heterojunctions with single crystals interfaced together is highlighted, with a focus on the advances in the efficient strategies for fabricating high‐quality heterostructures and exploring the resulting devices from the viewpoint of both their fundamental physics and electronic applications.
Conspectus Single crystals of organic semiconductors (OSCs) are believed to have both high mobility and intrinsic flexibility, making them promising candidates for flexible electronic/optoelectronic ...applications and being consistently pursued by researchers. The van der Waals force in OSC enables low-temperature solution processing of single crystals, but the relatively weak binding energy brings challenges in forming large, uniform, and defect-free single crystals. To promote the study on OSC single crystals, a generalized method that grows high-quality crystals in an easy-to-handle, time/resource-saving, and repeatable manner is apparently necessary. In 2012, Li et al. developed a droplet-pinned crystallization (DPC) method that uses a rather simple strategy to create a steadily receding contact line for the growth of OSC single crystals. Instead of setting up expensive equipment, controlling strict deposition parameters, or waiting for days or weeks for countable crystal seeds, the DPC method offers a time- and cost-effective way to obtain OSC single crystals for further study of the tendency of crystallization, single-crystal mobility, and molecular packing information. The DPC method is primarily a powerful tool for studying the charge-transport mechanisms in OSC single crystals. In pioneering work, high-mobility single crystals of both p-type 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) and n-type C60 materials were obtained. Driven by the demands from practical applications, we then focused on the general lagging of electron mobility in OSC materials. The ambipolar property of TIPS-PEN was studied, and a strong correlation between electron mobility and polar species (polar solvent residuals and surface hydroxyl groups) was observed. The latter further guided the harvest of electron mobility in a series of OSC materials. Undoubtfully, the facile DPC method accelerated these studies by providing a time-efficient, reliable, and repeatable testing platform. Additionally, flexibility on OSC materials and solvents, where not only one-component but also binary systems were allowed, is another critical integrity of the DPC method. The m-xylene/carbon tetrachloride binary solvent was proven to be efficient for growing ribbon-like C60 single crystals rather than needle-like crystals from typical one-component solvents. Afterward, a variety of OSC materials (including p-type, n-type, and ambipolar ones) and a series of solvents (including aromatic, aliphatic, and polar ones) were studied. The crystallization of OSC single crystals was primarily found at either the top liquid–air interface or the bottom solid–liquid interface. The interactions between OSC molecules and substrate surfaces were deduced as the qualitative determining factor. By utilizing the top interface crystallization, the two-step sequential deposition of single-crystalline OSC heterojunctions was enabled. Moreover, by selecting appropriate pairs of OSC materials that crystallize at separate interfaces, the facile one-step formation of single-crystalline OSC heterojunctions was achieved. The OSC single crystals and heterojunctions (including horizontal, vertical, and bulk heterojunctions) thereof exhibit promising potentials in circuits, photovoltaics, and photodiodes and would probably provide new insights for the future development of organic electronics.
The survivability of living organisms relies critically on their ability to self-heal from damage in unpredictable situations and environmental variability. Such abilities are most important in ...external facing organs such as the mammalian skin. However, the properties of bulk elemental materials are typically unable to perform self-repair. Consequently, most conventional smart electronic devices today are not designed to repair themselves when damaged. Thus, inspired by the remarkable capability of self-healing in natural systems, smart self-healing materials are being intensively researched to mimic natural systems to have the ability to partially or completely self-repair damages inflicted on them. This exciting area of research could potentially power a sustainable and smart future.
Detecting circularly polarized light (CPL) signals is the key technique in many advanced sensing technologies. Over recent decades, many efforts have been devoted to both the material design and the ...device engineering of CPL photodetectors. CPL detectors with different sensing wavelengths have distinct applications in bio-imaging, drug discovery, and information encryption. In this review, we first introduce the working principle of state-of-the-art CPL photodetectors followed by a general material design strategy. We then systematically summarize the recent progress on the chiral materials developed for CPL detection, including inorganic metamaterials, organics, hybridized materials,
etc.
We compare and analyse the photocurrent dissymmetry factors of these systems and provide perspectives on strategies to improve the dissymmetry factors and extend the detection wavelength. We believe that the information we include in this review would attract broader interest from researchers working on different aspects of organic and hybridized semiconductor materials and devices.
Detecting circularly polarized light is central to many advanced sensing technologies. We summarize the recent progress on the chiral materials developed for CPL detection and provide perspectives on strategies to improve the dissymmetry factors.
A large array of proxy records
suggests that the “4.2 ka event” marks an approximately
300-year long period (∼3.9 to 4.2 ka) of
major climate change across the globe. However, the climatic ...manifestation of
this event, including its onset, duration, and termination, remains less
clear in the Indian summer monsoon (ISM) domain. Here, we present new oxygen
isotope (δ18O) data from a pair of speleothems (ML.1 and ML.2)
from Mawmluh Cave, Meghalaya, India, that provide a high-resolution record of
ISM variability during a period (∼3.78 and 4.44 ka) that fully
encompasses the 4.2 ka event. The sub-annually to annually resolved ML.1
δ18O record is constrained by 18 230Th dates with an
average dating error of ±13 years (2σ) and a resolution of ∼40 years, which allows us to characterize the ISM variability with
unprecedented detail. The inferred pattern of ISM variability during the
period contemporaneous with the 4.2 ka event shares broad similarities and
key differences with the previous reconstructions of ISM from the Mawmluh
Cave and other proxy records from the region. Our data suggest that the ISM
intensity, in the context of the length of our record, abruptly decreased at
∼4.0 ka (∼±13 years), marking the onset of a multi-centennial
period of relatively reduced ISM, which was punctuated by at least two
multi-decadal droughts between ∼3.9 and 4.0 ka. The latter stands out
in contrast with some previous proxy reconstructions of the ISM, in which the
4.2 ka event has been depicted as a singular multi-centennial drought.
ABSTRACT
Previous research has shown that speleothems from the northern rim of the European Alps captured submillennial‐scale climate change during the last glacial period with exceptional ...sensitivity and resolution, mimicking Greenland ice‐core records. Here we extend this so‐called NALPS19 record across the Late Glacial using two stalagmites which grew continuously into the Holocene. Both specimens show the same high‐amplitude δ18O signal as Greenland ice cores down to decadal resolution. The start of the warming at the onset of the equivalent of Greenland Interstadial (GI) GI‐1e at 14.66 ± 0.18 ka agrees with the North Greenland Ice Core Project (NGRIP) (14.64 ± 0.28 ka) and comprised a temperature rise of about 5–6 °C. The transition from the equivalent of GI‐1a into the equivalent of Greenland Stadial (GS) GS‐1 (broadly equivalent to the Younger Dryas) commenced at 13.02 ± 0.13 ka which is consistent with NGRIP (12.80 ± 0.26 ka) within errors. The onset of the Holocene started at 11.78 ± 0.14 ka (11.65 ± 0.10 ka at NGRIP) and involved a warming of about 4–5 °C. In contrast to δ18O, δ13C values show no response to (sub)millennial climate shifts due to strong rock‐buffering and only record a long‐term trend of soil development starting with the rapid warming at 14.7 ka.
The Younger Dryas (YD), arguably the most widely studied millennial-scale extreme climate event, was characterized by diverse hydroclimate shifts globally and severe cooling at high northern ...latitudes that abruptly punctuated the warming trend from the last glacial to the present interglacial. To date, a precise understanding of its trigger, propagation, and termination remains elusive. Here, we present speleothem oxygen-isotope data that, in concert with other proxy records, allow us to quantify the timing of the YD onset and termination at an unprecedented subcentennial temporal precision across the North Atlantic, Asian Monsoon-Westerlies, and South American Monsoon regions. Our analysis suggests that the onsets of YD in the North Atlantic (12,870 ± 30 B.P.) and the Asian Monsoon-Westerlies region are essentially synchronous within a few decades and lead the onset in Antarctica, implying a north-to-south climate signal propagation via both atmospheric (decadal-time scale) and oceanic (centennial-time scale) processes, similar to the Dansgaard–Oeschger events during the last glacial period. In contrast, the YD termination may have started first in Antarctica at ∼11,900 B.P., or perhaps even earlier in the western tropical Pacific, followed by the North Atlantic between ∼11,700 ± 40 and 11,610 ± 40 B.P. These observations suggest that the initial YD termination might have originated in the Southern Hemisphere and/or the tropical Pacific, indicating a Southern Hemisphere/tropics to North Atlantic–Asian Monsoon-Westerlies directionality of climatic recovery.
We present new high‐resolution oxygen isotope (δ18O) records from three NW African speleothems located at ~31°N. The present‐day rainfall patterns at 31°N in NW Africa are linked to negative winter ...North Atlantic Oscillation phases. However, on multimillennial time scales, our δ18O records, together with other hydroclimate records, provide new evidence of humid conditions during the mid‐Holocene, a period that was presumably characterized by arid climate. Thus, the apparent increase in moisture during the mid‐Holocene is interpreted better as an increase in summer rainfall. This is most likely linked to the expansion of the West African summer monsoon fringe during the African Humid Period, which terminated in our record abruptly around 4 Kyr BP. The temporospatial difference with speleothem records from N Morocco suggests that the High‐Atlas Mountains might have been a topographic barrier to further expansion of the West African summer monsoon fringe into higher latitudes.
Plain Language Summary
The Holocene African Humid Period in North Africa, characterized by the expansion of vegetation into the Green Sahara, has been linked to the intensification of the West African summer monsoon (WASM). However, the temporospatial pattern of the African Humid Period, especially the northernmost expansion of the WASM, remain a matter of controversy, largely owing to the lack of precisely dated and high‐resolution paleoclimatic records. This study presents new high‐resolution paleoclimate data based on speleothem oxygen isotope records from a key site at ~31°N in NW Africa. Our data suggest that the WASM expanded to 31°N in NW Africa during the mid‐Holocene and terminated abruptly at 4 Kyr BP.
Key Points
Holocene rainfall variability in NW Africa is inferred from precisely dated and high‐resolution speleothem δ18O records
The West African summer monsoon expanded to 31°N in NW Africa during the mid‐Holocene
The African Humid Period ended with an abrupt interval of megadrought around 4 Kyr BP in NW Africa
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