Non-fullerene acceptors have recently attracted tremendous interest because of their potential as alternatives to fullerene derivatives in bulk heterojunction organic solar cells. However, the power ...conversion efficiencies (PCEs) have lagged far behind those of the polymer/fullerene system, mainly because of the low fill factor (FF) and photocurrent. Here we report a novel perylene bisimide (PBI) acceptor, SdiPBI-Se, in which selenium atoms were introduced into the perylene core. With a well-established wide-band-gap polymer (PDBT-T1) as the donor, a high efficiency of 8.4% with an unprecedented high FF of 70.2% is achieved for solution-processed non-fullerene organic solar cells. Efficient photon absorption, high and balanced charge carrier mobility, and ultrafast charge generation processes in PDBT-T1:SdiPBI-Se films account for the high photovoltaic performance. Our results suggest that non-fullerene acceptors have enormous potential to rival or even surpass the performance of their fullerene counterparts.
Two kinds of conjugated C 3-symmetric perylene dyes, namely, triperylene hexaimides (TPH) and selenium-annulated triperylene hexaimides (TPH-Se), are efficiently synthesized. Both TPH and TPH-Se have ...broad and strong absorption in the region 300–600 nm together with suitable LUMO levels of about −3.8 eV. Single-crystal X-ray diffraction studies show that TPH displays an extremely twisted three-bladed propeller configuration and a unique 3D network assembly in which three PBI subunits in one TPH molecule have strong π–π intermolecular interactions with PBI subunits in neighboring molecules. The integration of selenophene to TPH endows TPH-Se with a more distorted propeller configuration and a more compact 3D network assembly due to the Se···O interactions. A single-crystal transistor confirms that both TPH and TPH-Se possess good electron-transport ability. TPH and TPH-Se acceptor-based solar cells show high power conversion efficiency of 8.28% and 9.28%, respectively, which mainly results from the combined properties of broad and strong absorption ability, appropriate LUMO level, desirable aggregation, high electron mobility, and good film morphology with the polymer donor.
Li‐chalcogen batteries, especially the Li–S batteries (LSBs), have received paramount interests as next generation energy storage techniques because of their high theoretical energy densities. ...However, the associated challenges need to be overcome prior to their commercialization. Elemental selenium, another chalcogen member, would be an attractive alternative to sulfur owing to its higher electronic conductivity, comparable capacity density, and moreover, excellent compatibility with carbonate electrolytes. Unlike LSBs, the research and development of Li–Se batteries (LSeBs) have garnered burgeoning attention but are still in their infant stage, where a comprehensive yet in‐depth overview is highly imperative to guide future research. Herein, a critical review of LSeBs, in terms of the underlying mechanisms, cathode design, blocking layer engineering, and emerging solid‐state electrolytes is provided. First, the electrolyte‐dependent electrochemistry of LSeBs is discussed. Second, the advances in Se‐based cathodes are comprehensively summarized, especially highlighting the state‐of‐the‐art SexSy cathodes, and mainly focusing on their structures, compositions, and synthetic strategies. Third, the versatile separators/interlayers optimization and interface regulation are outlined, with a particular focus on the emerging solid‐state electrolytes for advanced LSeBs. Last, the remaining challenges and research orientations in this booming field are proposed, which are expected to motivate more insightful works.
Li–Se batteries (LSeBs) have garnered intensive attention since the Se cathode possesses high capacity and electronic conductivity. LSeBs experience a solid‐to‐solid transformation accompanied by side reactions in carbonate electrolytes but multiphase conversion in ether‐based ones. The advances for cathode design, blocking layer engineering, and emerging solid‐state electrolytes are summarized. The future research directions are also outlined to motivate further insightful work.
Lithium–chalcogen batteries are an appealing choice for high‐energy‐storage technology. However, the traditional battery that employs liquid electrolytes suffers irreversible loss and shuttle of the ...soluble intermediates. New batteries that adopt Li+‐conductive polymer electrolytes to mitigate the shuttle problem are hindered by incomplete discharge of sulfur/selenium. To address the trade‐off between energy and cycle life, a new electrolyte is proposed that reconciles the merits of liquid and polymer electrolytes while resolving each of their inferiorities. An in situ interfacial polymerization strategy is developed to create a liquid/polymer hybrid electrolyte between a LiPF6‐coated separator and the cathode. A polymer‐gel electrolyte in situ formed on the separator shows high Li+ transfer number to serve as a chemical barrier against the shuttle effect. Between the gel electrolyte and the cathode surface is a thin gradient solidification layer that enables transformation from gel to liquid so that the liquid electrolyte is maintained inside the cathode for rapid Li+ transport and high utilization of active materials. By addressing the dilemma between the shuttle chemistry and incomplete discharge of S/Se, the new electrolyte configuration demonstrates its feasibility to trigger higher capacity retention of the cathodes. As a result, Li–S and Li–Se cells with high energy and long cycle lives are realized, showing promise for practical use.
The rational reconfiguration of an electrolyte enabled by an in situ interfacial polymerization strategy is demonstrated. This strategy endows Li–S and Li–Se batteries with high capacity, stable cycling, and excellent rate performances simultaneously, and may become a new pathway toward the large‐scale and cost‐effective applications of future Li metal batteries.
Selenium is a semimetallic element lying in group XVI of the periodic table with its chemical properties resembling sulfur. But owing to its relatively low electronegativity and large atomic radius ...compared with sulfur, selenium also shows unique properties. This feature endows selenium-containing compounds with high reactivity and sensitivity. Although organic selenium chemistry has been developing very fast, the successful introduction of selenium into polymer science is rather scarce. Fortunately, we have seen a drastic rising trend in the area of selenium-containing polymers over the past decade. In this Perspective, the synthetic routes of selenium-containing polymers are summarized, and their unique stimuli-responsive properties are elaborated on, together with their diverse applications in the field of adaptive and biomedical materials.
Chiral electrophilic selenium catalysts have been applied to catalytic asymmetric transformations of alkenes over the past two decades. However, highly enantioselective reactions with a broad ...substrate scope have not yet been developed. We report the first successful example of this reaction employing a catalyst based on a rigid indanol scaffold, which can be easily synthesized from a commercially available indanone. The reaction efficiently converts β,γ-unsaturated carboxylic acids into various enantioenriched γ-butenolides under mild conditions.
Lithium-selenium (Li–Se) batteries represent a promising energy storage system due to the relatively high electronic conductivity and high volumetric energy density of Se as a cathode. The design of ...porous carbon with tunable structure and low cost is a key to enabling Se cathodes for high-performance Li–Se batteries. In this study, hierarchically microporous activated carbon (AC) was fabricated from waste coffee grounds through a carbonization and KOH-activation process. Despite the simple synthesis process, the optimized AC (AC-700) had a high surface area of 1355 m2 g−1 and a large microspore volume of 0.52 cm³ g−1. The Se/AC-700 cathode showed a reversible capacity of 655 mAh g−1 after 100 cycles at 0.1C in Li–Se batteries based on a carbonate electrolyte. Moreover, the Se/AC-700 cathode demonstrated excellent cyclic performance over 400 cycles without appreciable capacity decay. The main reason for the good battery performance was attributed to fast electron transfer and Li-ion diffusion in Se confined in the microporous carbon of AC-700. It is expected that this work will shed light on the development of low-cost and stable Se cathodes for high-energy Li–Se batteries.
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•Microporous carbon is synthesized from waste coffee grounds (WCG).•WCG-derived carbon is used as a Se cathode host in Li–Se batteries.•Se/carbon cathode exhibits high a reversible capacity and long cycling life.•Micropores in carbon are key to enabling fast e− transfer and Li+ diffusion in Se.
Lower-cost thermoelectricsThermoelectric materials convert heat to electricity, making them attractive for heat harvesting or cooling applications. However, many high-performance thermoelectrics are ...made of expensive or toxic materials. He et al. found that a material composed of primarily tin and sulfur could be optimized to have relatively good thermoelectric properties. Introducing about 10% selenium to tin sulfide helped tune these properties by electronic band manipulation. This material is a step toward more earth-abundant, less toxic, and lower-cost thermoelectrics than the telluride-based materials currently in use.Science, this issue p. 1418Thermoelectric technology allows conversion between heat and electricity. Many good thermoelectric materials contain rare or toxic elements, so developing low-cost and high-performance thermoelectric materials is warranted. Here, we report the temperature-dependent interplay of three separate electronic bands in hole-doped tin sulfide (SnS) crystals. This behavior leads to synergistic optimization between effective mass (m*) and carrier mobility (μ) and can be boosted through introducing selenium (Se). This enhanced the power factor from ~30 to ~53 microwatts per centimeter per square kelvin (μW cm−1 K−2 at 300 K), while lowering the thermal conductivity after Se alloying. As a result, we obtained a maximum figure of merit ZT (ZTmax) of ~1.6 at 873 K and an average ZT (ZTave) of ~1.25 at 300 to 873 K in SnS0.91Se0.09 crystals. Our strategy for band manipulation offers a different route for optimizing thermoelectric performance. The high-performance SnS crystals represent an important step toward low-cost, Earth-abundant, and environmentally friendly thermoelectrics.
High energy density batteries and high power density supercapacitors have attracted much attention because they are crucial to the power supply of future portable electronic devices, electric ...automobiles, unmanned aerial vehicles, etc. The electrode materials are key components for batteries and supercapacitors, which influence the practical energy and power density. Metal-organic frameworks possessing unique morphology, high specific surface area, functional linkers, and metal sites are excellent electrode materials for electrochemical energy storage devices. Herein, we review and comment on recent progress in metal-organic framework-based lithium-ion batteries, sodium-ion batteries, lithium-air batteries, lithium-sulfur/selenium batteries, and supercapacitors. Future perspectives and directions of metal-organic framework-based electrochemical energy storage devices are put forward on the basis of theoretical knowledge from the reported literature and our experimental experience.
Embedding the fragmented selenium into the micropores of carbon host has been regarded as an effective strategy to change the Li–Se chemistry by a solid–solid mechanism, thereby enabling an excellent ...cycling stability in Li–Se batteries using carbonate electrolyte. However, the effect of spatial confinement by micropores in the electrochemical behavior of carbon/selenium materials remains ambiguous. A comparative study of using both microporous (MiC) and mesoporous carbons (MeC) with narrow pore size distribution as selenium hosts is herein reported. Systematic investigations reveal that the high Se utilization rate and better electrode kinetics of MiC/Se cathode than MeC/Se cathode may originate from both its improved Li+ and electronic conductivities. The small pore size (<1.35 nm) of the carbon matrices not only facilitates the formation of a compact and robust solid‐electrolyte interface (SEI) with low interfacial resistance on cathode, but also alters the insulating nature of Li2Se due to the emergence of itinerant electrons. By comparing the electrochemical behavior of MiC/Se cathode and the matching relationship between the diameter of pores and the dimension of solvent molecules in carbonate, ether, and solvate ionic liquid electrolyte, the key role of SEI film in the operation of C/Se cathode by quasi‐solid‐solid mechanism is also highlighted.
For microporous carbon/Se cathode in carbonate electrolyte, micropores facilitate the formation of thin LiF‐rich solid electrolyte interphase on the C/Se cathode, allowing fast Li+ conduction. The nanoconfinement of micropores can generate the itinerant electrons and alter the insulating nature of Li2Se.
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