Fused‐ring electron acceptors have made significant progress in recent years, while the development of fully non‐fused ring acceptors has been unsatisfactory. Here, two fully non‐fused ring ...acceptors, o‐4TBC‐2F and m‐4TBC‐2F, were designed and synthesized. By regulating the location of the hexyloxy chains, o‐4TBC‐2F formed planar backbones, while m‐4TBC‐2F displayed a twisted backbone. Additionally, the o‐4TBC‐2F film showed a markedly red‐shifted absorption after thermal annealing, which indicated the formation of J‐aggregates. For fabrication of organic solar cells (OSCs), PBDB‐T was used as a donor and blended with the two acceptors. The o‐4TBC‐2F‐based blend films displayed higher charge mobilities, lower energy loss and a higher power conversion efficiency (PCE). The optimized devices based on o‐4TBC‐2F gave a PCE of 10.26 %, which was much higher than those based on m‐4TBC‐2F at 2.63 %, and it is one of the highest reported PCE values for fully non‐fused ring electron acceptors.
Two fully non‐fused acceptors are precisely designed and easily prepared. The side chain encapsulation can induce a planar molecular backbone conformation, endowing the acceptor with broad light absorption. Thermal annealing promotes molecular rearrangement to form J‐aggregates with even broader absorption and higher absorption coefficient. A PCE over 10 % is one of the highest PCE for fully non‐fused ring acceptors.
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Three regioregular benzodithiophene‐based donor–donor (D–D)‐type polymers (PBDTT, PBDTT1Cl, and PBDTT2Cl) are designed, synthesized, and used as donor materials in organic solar cells (OSCs). Because ...of the weak intramolecular charge‐transfer effect, these polymers exhibit large optical bandgaps (>2.0 eV). Among these three polymers, PBDTT1Cl exhibits more ordered and closer molecular stacking, and its devices demonstrate higher and more balanced charge mobilities and a longer charge‐separated state lifetime. As a result of these comprehensive benefits, PBDTT1Cl‐based OSCs give a very impressive power conversion efficiency (PCE) of 17.10% with a low nonradiative energy loss (0.19 eV). Moreover, PBDTT1Cl also possesses a low figure‐of‐merit value and good universality to match with different acceptors. This work provides a simply and efficient strategy to design low‐cost high‐performance polymer donor materials.
Three D–D type wide‐bandgap donor polymers (PBDTT, PBDTT1Cl, and PBDTT2Cl) are designed and facilely synthesized. Organic solar cells (OSCs) based on PBDTT1Cl exhibit a high power conversion efficiency of 17% and a low nonradiative energy loss of 0.19 eV. In addition, PBDTT1Cl has a very low figure‐of‐merit and good universality, indicating its potential as a low‐cost polymer donor for high‐performance OSCs.
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Rechargeable Li‐O2 batteries have aroused much attention for their high energy density as a promising battery technology; however, the performance of the batteries is still unsatisfactory. Lithium ...anodes, as one of the most important part of Li‐O2 batteries, play a vital role in improving the cycle life of the batteries. Now, a very simple method is introduced to produce a protective film on lithium surface via chemical reactions between lithium metals and 1,4‐dioxacyclohexane. The film is mainly composed of ethylene oxide monomers and endows Li‐O2 batteries with enhanced cycling stability. The film could effectually reduce the morphology changes and suppress the parasitic reactions of lithium anodes. This simple approach provides a new strategy to protect lithium anodes in Li‐O2 batteries.
Protective coating: The stability of lithium anodes plays a vital role in improving the cycle life of Li‐O2 batteries. A convenient method is presented to produce a film on a lithium surface by chemical reactions between lithium metal and 1,4‐dioxacyclohexane. The protective film could reduce the morphology changes and suppress the parasitic reactions of lithium anodes and endow Li‐O2 batteries with enhanced cycling stability.
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Three nonfused ring electron acceptors (NFREAs), namely, 3TT‐C2‐F, 3TT‐C2‐Cl, and 3TT‐C2, are purposefully designed and synthesized with the concept of halogenation. The incorporation of F or/and Cl ...atoms into the molecular structure (3TT‐C2‐F and 3TT‐C2‐Cl) enhances the π–π stacking, improves electron mobility, and regulates the nanofiber morphology of blend films, thus facilitating the exciton dissociation and charge transport. In particular, blend films based on D18:3TT‐C2‐F demonstrate a high charge mobility, an extended exciton diffusion distance, and a well‐formed nanofiber network. These factors contribute to devices with a remarkable power conversion efficiency of 17.19%, surpassing that of 3TT‐C2‐Cl (16.17%) and 3TT‐C2 (15.42%). To the best of knowledge, this represents the highest efficiency achieved in NFREA‐based devices up to now. These results highlight the potential of halogenation in NFREAs as a promising approach to enhance the performance of organic solar cells.
Three nonfused ring electron acceptors (3TT‐C2‐F, 3TT‐C2‐Cl, and 3TT‐C2) are designed and synthesized with the concept of halogenation. Among them, the fluorinated acceptor 3TT‐C2‐F based devices can deliver the champion power conversion efficiency of over 17% due to enhanced the π–π stacking, improved the electron mobility, etc.
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Synthetic hydrogels or water-containing polymeric materials are much inferior to biological tissues and solid plastics in many aspects of mechanical properties; it is a great challenge to develop ...hydrogels with mechanical properties comparable with or even superior to those of biological tissues and plastics. Here, we report a type of super-strong and tough hydrogen-bonded poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) hydrogel by immersing as-prepared PVA hydrogels in aqueous PAA solutions and then cold-drawing the hydrogels to different strains. The immersing process introduces PAA chains into the PVA hydrogels, which increases the cross-linking density by hydrogen bonding and hence, much improved mechanical properties and low water contents (35.9-40.2 wt%) are observed. The cold-drawing orients the polymer chains, which enables the formation of more and stronger hydrogen bonds. The mechanical properties of cold-drawn gels are dramatically enhanced, with tensile strength and elastic modulus up to 140 and 100 MPa, respectively; also, super-high toughness (117 MJ m
) and fracture energy (101 kJ m
) are obtained. Very impressively, the ultra-high tensile strengths of the cold-drawn hydrogels are superior to those of biological tissues and most solid engineered plastics. Characterizations and comparative studies prove that the enhancement of mechanical properties is mainly due to the formation of more hydrogen bonding rather than the loss of water or the change in crystallinity. This study provides a new strategy for preparing super-strong physically cross-linked hydrogels and other polymeric materials. This super-strong and tough hydrogel may find potential applications in biomedical and load-bearing fields.
A novel type of polymeric material with tunable mechanical properties is fabricated from polymers and small molecules that can form hydrogen‐bonded intermolecular complexes (IMCs). In this work, ...poly(vinyl alcohol) (PVA)–glycerol hydrogels are first prepared, and then they are dried to form IMCs. The tensile strengths and moduli of IMCs decrease dramatically with increasing glycerol content, while the elongations increase gradually. The mechanical properties are comparable with or even superior to those of common engineering plastics and rubbers. The IMCs with high glycerol content also show excellent flexibility and cold‐resistance at subzero temperatures. Cyclic tensile and stress relaxation tests prove that there is an effective energy dissipation mechanism in IMCs and dynamic mechanical analysis confirms their physical crosslinking nature. FTIR and NMR characterizations prove the existence of hydrogen bonding between glycerol and PVA chains, which suppresses the crystallization of PVA from X‐ray diffraction measurement. These PVA–glycerol IMCs may find potential applications in barrier films, biomedical packaging, etc., in the future.
A novel type of polymeric material with tunable mechanical properties from plastics to rubber‐like materials is fabricated from polymers and small molecules that can form hydrogen‐bonded intermolecular complexes (IMCs). The mechanical properties of the poly(vinyl alcohol)–glycerol IMCs are comparable with or even superior to those of common engineering plastics and rubbers.
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Planar building block B2TCl with C2V symmetry configuration is designed to prepare polymer donors (PB2TCl‐o and PB2TCl‐i) with good solubility in non‐halogenated solvents. When blended with ...BTP‐ec9‐4F, PB2TCl‐o‐based devices processed by 1,2‐dimethylbenzene (o‐DMB) give a power conversion efficiency (PCE) of 15.10% with a Voc of 0.89 V, a Jsc of 24.37 mA cm–2, and an fill factor of 69.69%. Semitransparent OSCs based on PB2TCl‐o:BTP‐ec9‐4 can afford a PCE of 9.09% with an average visible transmittance (AVT) of 23.9% and an AT of 24.2%. B2TCl‐o is also used as a third component to prepare random terpolymers PW1 and PW2. Using o‐DMB as the processing solvent, PW1 and PW2‐based devices give improved PCEs of 16.26% and 17.19%, respectively, which are much higher than the parent polymers (PM6 and D18). This work provides a versatile building block B2TCl‐o for the preparation of non‐halogen solvent processable high‐performance polymer donor materials.
Non‐halogenated solvent processable polymer donors are prepared using planar building block B2TCl‐o with C2V symmetry. The device gives a power conversion efficiency (PCE) of 15.10% with 1,2‐dimethylbeneze as processing solvent and the corresponding semitransparent device can afford a PCE of 9.09%. Terpolymers PW1 and PW2 with B2TCl‐o as the third component can deliver higher PCEs of 16.26% and 17.19%, respectively.
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In recent decades, electrocatalysis has become an important research hotspot in energy storage and conversion technologies due to the persistently increasing energy and environmental issues. ...Nanostructured carbon materials with excellent electrical conductivity, competitive activity, and relatively high chemical stability are extensively studied as either electrocatalysts or substrates to support metal‐based catalysts. Especially, when used as supporting substrates for metal‐based catalysts, carbon‐based materials can not only effectively promote the dispersion of metals and even lead to single‐atom catalysts but also lead to prominent synergistic effects for enhanced activity. This review sheds light on state‐of‐the‐art carbon‐based materials employed as supporting substrates for selected electrocatalytic processes involving H2/O2/CO2/N2. By combining experimental explorations with theoretical computations, clear insight is elaborately afforded into the fundamental relationship between electrocatalytic activity and metal–substrate interaction, in order to disclose some clues for electrocatalyst design. Finally, the remaining challenges and perspectives are discussed for the future development of carbon‐supported electrocatalysts.
This review mainly focuses on state‐of art carbon‐based materials involving carbon, C3N4, C2N, and B4C employed as supporting substrates for electrocatalysis. Computations complement the deficiency of experimental techniques, elucidating the electrocatalytic mechanisms through electron transfer, adsorption energy, precise active sites, and metal–substrate interaction.
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Li‐CO2 batteries could skillfully combine the reduction of “greenhouse effect” with energy storage systems. However, Li‐CO2 batteries still suffer from unsatisfactory electrochemical performances and ...their rechargeability is challenged. Here, it is reported that a composite of Ni nanoparticles highly dispersed on N‐doped graphene (Ni‐NG) with 3D porous structure, exhibits a superior discharge capacity of 17 625 mA h g−1, as the air cathode for Li‐CO2 batteries. The batteries with these highly efficient cathodes could sustain 100 cycles at a cutoff capacity of 1000 mA h g−1 with low overpotentials at the current density of 100 mA g−1. Particularly, the Ni‐NG cathodes allow to observe the appearance/disappearance of agglomerated Li2CO3 particles and carbon thin films directly upon discharge/charge processes. In addition, the recycle of CO2 is detected through in situ differential electrochemical mass spectrometry. This is a critical step to verify the electrochemical rechargeability of Li‐CO2 batteries. Also, first‐principles computations further prove that Ni nanoparticles are active sites for the reaction of Li and CO2, which could guide to design more advantageous catalysts for rechargeable Li‐CO2 batteries.
A composite of Ni nanoparticles highly dispersed on N‐doped graphene is prepared as the air cathode for Li‐CO2 batteries, with high discharge capacity and excellent cyclic stability. The cathode allows to observe the morphological evolution of discharge products directly and reversible consumption and evolution of CO2, and then the reversibility of electrochemical reactions could well be understood in Li‐CO2 batteries.
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Comprehensive Summary
By simplifying the π‐bridge unit, a nonfused ring electron acceptor (NFREA) BM‐2F was designed and synthesized with several high‐yield steps. The specific molecular structure ...features of BM‐2F are planar molecular backbone and out‐of‐plane side chain, which is favorable for charge transport and can suppress the over‐aggregation. BM‐2F based neat and blend films display obvious face‐on molecular orientation. Specially, D18:BM‐2F based blend film can form good bicontinuous interpenetrating network. More excitingly, a power conversion efficiency of 16.15% was achieved with D18:BM‐2F based photovoltaic devices, which is the highest one based on NFREAs. Our researches manifest that NFREA is a promising direction for low‐cost and high‐performance organic solar cells.
We designed a novel nonfused ring electron acceptor (BM‐2F), which can be obtained by four‐step high‐yield synthetic steps and is of 3D molecular structure. With D18 as polymer donor, the devices can afford a champion power conversion efficiency of 16.15% and display high FOM value, demonstrating great potential for future commercial application.
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