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Energy loss caused by exciton binding energy (

To reduce synthetic cost of the classic fluorinated bithienyl benzodithiophene (BDTT-F) unit, here, an alpha-fluorinated bithienyl benzodithiophene unit, namely, α-BDTT-F (F atom in the α position of the lateral thiophene unit), is developed by the isomerization strategy of exchanging the positions of the F atom and flexible alkyl chain on the lateral thiophene unit of the BDTT-F unit. The α-BDTT-F unit was synthesized with less synthetic steps, higher synthetic yield, and less purification times from the same raw materials as those of the BDTT-F unit, thus with low synthetic cost. Theoretical calculation indicates that the α-BDTT-F unit possesses a similar twisted conformation and electronic structures as those of the BDTT-F unit. The α-BDTT-F-based polymer α-PBQ10 exhibits similar light absorption and energy levels as those of the corresponding BDTT-F-based polymer PBQ10 but marginally increased molecular aggregation and stronger hole transport than PBQ10. In consequence, the α-PBQ10:Y6-based polymer solar cell demonstrates a slightly enhanced power conversion efficiency (PCE) of 16.26% compared with that of the PBQ10:Y6-based device (PCE = 16.23%). Also, the PCE is further improved to 16.77% through subtle microscopic morphology regulation of the photoactive layer with the fullerene derivative indene-C60 bisadduct as the third component. This work provides new ideas for the design of low-cost and high-efficiency photovoltaic molecules.

Flexible zinc-ion hybrid capacitors (ZIHCs) based on hydrogel electrolytes are an up-and-coming and highly promising candidate for potential large-scale energy storage due to their combined complementary advantages of zinc batteries and capacitors. However, the freezing induces a sharp drop in conductivity and mechanical property with tremendous compromise of the interfacial adhesion, thereby severely impeding the low-temperature application of such flexible ZIHCs. To achieve the flexible ZIHCs with excellent low-temperature adaptability, an antifreezing and self-adhesive polyzwitterionic hydrogel electrolyte (PZHE) is engineered via a self-catalytic nano-reinforced strategy, affording unparalleled conductivity and robust interfacial adhesion, together with superhigh mechanical strength over a broad temperature ranging from 25 to -60 °C. Meanwhile, the water-in-salt-type PZHE filled with ZnCl2 can provide ion migration channels to enhance the reversibility of Zn metal electrodes, thus greatly reducing side reactions and extending the cycling life. With distinctive integrated merits of the water-in-salt type PZHE, the as-built ZIHCs deliver a high-level energy density of 80.5 Wh kg-1, a desired specific capacity of 81.5 mAh g-1, along with a long-duration cycling lifespan (100 000 cycles) with 84.6% capacity retention at -40 °C, even outperforming the state-of-the-art ZIHCs at room temperature. More encouragingly, the extraordinary temperature-adaptability for both electrochemical and mechanical performance under severe mechanical challenges is achieved for the flexible ZIHCs at extremely low temperature. Noticeably, the ZIHC is also capable of operating in an ice-water bath and vacuum. It is believed that this strategy makes contributions to inspire the design and application of high-performance PZHEs in fields of flexible and wearable electronics that can work in extremely cold environments.

Herein, a new organic-inorganic hybrid cuprous iodide of [(Me)2-DABCO]Cu6I8 was prepared and structurally characterized with a novel three-dimensional (3D) [Cu6I8]2- framework. Significantly, this 3D cuprous iodide displays infrequent broadband red-to-near-infrared light emission (600-1000 nm) stemming from the radiative recombination of self-trapped excitons.

Unraveling the relationship between nanoscale morphology of active layers and chemical structures of organic semiconductor photovoltaic materials is crucially important for further advancing the development of all-small-molecule organic solar cells (SM-OSCs). Here, in order to delve into the effect of flexible side chains of small molecule donors on the photovoltaic properties of SM-OSCs, we synthesized two new small molecule donors substituted by different flexible alkyl chains (iso-octyl chains for SM1-EH and n-octyl chains for SM1-Oct). As a result, the two small molecules present different absorption properties, energy levels, and stacking characteristics. When blending with Y6 as an acceptor, the SM1-Oct-based SM-OSC demonstrated a higher PCE value of 11.73%, while the SM1-EH-based device presents a relatively poorer PCE value of 8.42%. In addition, the morphology analysis demonstrated that, compared with the SM1-EH:Y6 blend, the SM1-Oct:Y6 blend film displayed better molecular stacking properties with stronger multilevel diffraction and preferable phase separation, resulting in the higher hole mobility, more efficient charge separation efficiency, and better device performance. These results underline that reasonably adjusting the flexible alkyl chains of small molecule donors can be an effective approach to further advance the development of the SM-OSCs field.

Wrinkles are special surface corrugations in two-dimensional materials, which can be used to tune their electronic, optical, and chemical properties. There have been many studies focusing on the wr...

The application of conductive hydrogels in intelligent biomimetic electronics is a hot topic in recent years, but it is still a great challenge to develop the conductive hydrogels through a rapid fabrication process at ambient temperature. In this work, a versatile poly(acrylamide) @cellulose nanocrystal/tannic acid-silver nanocomposite (NC) hydrogel integrated with excellent stretchability, repeatable self-adhesion, high strain sensitivity, and antibacterial property, was synthesized via radical polymerization within 30 s at ambient temperature. Notably, this rapid polymerization was realized through a tannic acid-silver (TA-Ag) mediated dynamic catalysis system that was capable of activating ammonium persulfate and then initiated the free-radical polymerization of the acrylamide monomer. Benefiting from the incorporation of TA-Ag metal ion nanocomplexes and cellulose nanocrystals, which acted as dynamic connecting bridges by hydrogen bonds to efficiently dissipate energy, the obtained NC hydrogels exhibited prominent tensile strain (up to 4000%), flexibility, self-recovery, and antifatigue properties. In addition, the hydrogels showed repeatable adhesiveness to different substrates (e.g., glass, wood, bone, metal, and skin) and significant antibacterial properties, which were merits for the hydrogels to be assembled into a flexible epidermal sensor for long-term human-machine interfacial contact without concerns about the use of external adhesive tapes and bacterial breeding. Moreover, the remarkable conductivity (σ ∼ 5.6 ms cm-1) and strain sensitivity (gauge factor = 1.02) allowed the flexible epidermal sensors to monitor various human motions in real time, including huge movement of deformations (e.g., wrist, elbow, neck, shoulder) and subtle motions. It is envisioned that this work would provide a promising strategy for the rapid preparation of conductive hydrogels in the application of flexible electronic skin, biomedical devices, and soft robotics.

We observe sharp step-down discontinuities in the magnetic susceptibility of NH4H2PO4 and NH4H2PO4-d60 (60% deuterated) along the a- and c-axes occurring exactly at their antiferroelectric transiti...

Most ferroelectric crystals have their own set of unique characteristics, and ammonium sulfate (NH4)2SO4 is no exception. We report on two previously unidentified features in ammonium sulfate: (1) ...

Molecular frontier orbital energy level and aggregation behavior regulation of polymer donors are feasible ways to improve the photovoltaic performance of polymer solar cells (PSCs). Here, we desig...

In this work, three benzodithiophene-benzotriazole alternated wide band gap copolymers attaching symmetric or asymmetric conjugated side chains, namely, PDBTFBTA-2T, PBDTFTBA-TSi, and PBDTFBTA-2Si, were developed for efficient nonfullerene polymer solar cells. The symmetry effect of the side chains was investigated in detail on the overall properties of these donor polymers. The results demonstrated that the introduced siloxane functional groups showed less effect on the absorption and frontier orbital levels of the prepared polymers but had a significant effect on the miscibility between these polymer donors and the nonfullerene acceptor. When increasing the content of siloxane functional groups, the miscibility of the polymer donors and Y6 would be improved, leading to the decreased domain size and more mixed domains. Interestingly, the active blend based on PBDTFTBA-TSi with asymmetric side chains exhibited more balanced miscibility, carrier mobility, and phase separation, benefiting exciton diffusion and dissociation. Therefore, a champion power conversion efficiency (PCE) of 14.18% was achieved finally in PBDTFTBA-TSi devices, which was 20.6 and 19.0% higher than the symmetric counterparts of PBTFBTA-2T devices (PCE = 11.76%) and PBDTFBTA-2Si devices (PCE = 11.92%), respectively. This work highlights that the asymmetric side-chain engineering based on siloxane functional groups is a promising design strategy for high-performance polymer donor semiconductors.

Four new metal–organic frameworks, {[Zn(L)(dcdps)]}n (1), {Zn(L)(bdc)}n (2), {[Cd(L)(oba)]·0.5DMF}n (3), and {[Cd(L)(bdc)·2H2O]·2DMF}n (4) [L = 4,4′-(2,5-bis(methylthio)-1,4-phenylene)dipyridine; H...

Nucleobases detection is important in DNA sequencing, disease testing linked to genes, and disease treatment. In this work, the interactions of nonmetallic element (Si, P, Cl, Se) doped MoS2 monola...

Different types of magnetism arise mainly from how electrons move and interact with each other. In this work, we show how protons (H+) also exhibit magnetic behavior. We measured the magnetic susce...

In this work, the composite hydrogel toughening behaviors as manifested by strain rate-dependent viscoelastic properties and enhanced fracture mechanics, that is, suppressed catastrophic crack propagation with increased resistance, are systematically examined by using cellulose nanofibrils (CNFs) as fillers in the polyacrylamide (PAAm) matrix. The uniaxial deformation tests show that the tearing energy increases with crack velocity and becomes dominated by the viscoelastic energy dissipation in front of the crack tip. The creep dynamics of the composite hydrogels under a constant stress is examined, and the results indicate that the incorporation of the CNF pronouncedly suppresses the creep deformation. In addition, the microdeformation and failure mechanisms are analyzed through the observation of morphology of arrested crack tips and the damage zone by transmission electron microscopy and scanning electron microscopy. By aligning the CNF along the crack direction, it is possible to focus on the study of interfacial slip mechanics and identify the role of interfacial slip during the energy dissipation process. The results indicate that the CNFs are largely orientated parallel to the loading direction to maximize the energy dissipation, where the initiation of crack propagation is the primary fracture mechanism in composite hydrogels. The coarse feature on the composite fracture surface implies that the CNF initiates deflection of crack propagation fronts and thus increases the strain energy for continuation of the fracture. It is envisioned that with the incorporation of interdisciplinary strategies, one can rationally combine multiple approaches toward the creation of nanocomposite hydrogels with enhanced mechanical properties.

Silk fibroin (SF) based hydrogels are the focus of extensive research due to their ability to form complex hierarchical structures, as well as their biocompatibility and biodegradability. However, ...

Although self-healing gels with structural resemblance to biological tissues attract great attention in biomedical fields, it remains a dilemma for combination between fast self-healing properties and high mechanical toughness. On the basis of the design of dynamic reversible cross-links, we incorporate rigid tannic acid-coated cellulose nanocrystal (TA@CNC) motifs into the poly(vinyl alcohol) (PVA)-borax dynamic networks for the fabrication of a high toughness and rapidly self-healing nanocomposite (NC) hydrogel, together with dynamically adhesive and strain-stiffening properties that are particularly indispensable for practical applications in soft tissue substitutes. The results demonstrate that the obtained NC gels present a highly interconnected network, where flexible PVA chains wrap onto the rigid TA@CNC motifs and form the dynamic TA@CNC-PVA clusters associated by hydrogen bonds, affording the critical mechanical toughness. The synergetic interactions between borate-diol bonds and hydrogen bonds impart a typical self-healing behavior into the NC gels, allowing the dynamic cross-linked networks to undergo fast rearrangement in the time scale of seconds. Moreover, the obtained NC hydrogels not only mimic the main feature of biological tissues with the unique strain-stiffening behavior but also display unique dynamic adhesiveness to nonporous and porous substrates. It is expected that this versatile approach opens up a new prospect for the rational design of multifunctional cellulosic hydrogels with remarkable performance to expand their applications.

The precise control of stoichiometric balance and ionic defects on the surface of solution-processed perovskite is critical to the performance and stability of perovskite solar cells (pero-SCs). Here, we introduce a low-cost and stable conjugated donor polymer (PTQ10) as interfacial layer in the planar n-i-p structured pero-SCs. The polymer was applied to the perovskite intermediate phase before the thermal annealing. This treatment significantly reduced the loss of surface organic cation during thermal annealing. Importantly, the kinetics of phase conversion of perovskite was influenced, and perovskite crystal showed a more preferential orientation. Moreover, the polymer proved to be an effective hole extraction layer due to the proper energy alignment with perovskite. Finally, a champion power conversion efficiency of the planar pero-SCs was achieved at 21.2% with a high fill factor of 81.6%. The devices also showed great ambient and thermal stability. This work presents a facile way of perovskite surface control to achieve high-performance pero-SCs.

Developing hydrogels with enhanced mechanical properties has attracted broad attention in recent years. In this work, we propose a facile procedure to prepare tough composite hydrogels by incorporating silk microfibers (mSF) into alginate ionically cross-linked networks. The mSF gives rise to ionic bonds with Ca2+ and interfacial hydrogen bonds because of the carboxyl groups on the surface of mSF, and the neighboring alginate chains are interlinked by mSF, which synergistically led to efficient energy dissipation and prevention of stress concentration. The attained composite hydrogels show superior elastic modulus (1.58 MPa), tensile strength (1.60 MPa), and unique adaptive interface response. Moreover, the mechanical properties of the composite hydrogels can be tailored by the concentration of mSF and the time immersing the composite hydrogels in CaCl2 solution post-cross-linking. Intriguingly, the mechanical properties can be further improved through a prestretching methodology to align the alginate cha...

The remarkable progress in efforts to prepare conductive self-healing hydrogels mimicking human skin’s functions has been witnessed in recent years. However, it remains a great challenge to develop an integrated conductive gel combining excellent self-healing and mechanical properties, which is derived from their inherent compromise between the dynamic cross-links for healing and steady cross-links for mechanical strength. In this work, we design a tough, self-healing, and self-adhesive ionic gel by constructing synergistic multiple coordination bonds among tannic acid-coated cellulose nanocrystals (TA@CNCs), poly(acrylic acid) chains, and metal ions in a covalent polymer network. The incorporated TA@CNC acts as a dynamic connected bridge in the hierarchically porous network mediated by multiple coordination bonds, endowing the ionic gels the superior mechanical performance. Reversible nature of dynamic coordination interactions leads to excellent recovery property as well as reliable mechanical and elect...

We have demonstrated high-performance integrated perovskite/bulk-heterojunction (BHJ) solar cells due to the low carrier recombination velocity, high open circuit voltage (VOC), and increased light absorption ability in near-infrared (NIR) region of integrated devices. In particular, we find that the VOC of the integrated devices is dominated by (or pinned to) the perovskite cells, not the organic photovoltaic cells. A Quasi-Fermi Level Pinning Model was proposed to understand the working mechanism and the origin of the VOC of the integrated perovskite/BHJ solar cell, which following that of the perovskite solar cell and is much higher than that of the low bandgap polymer based organic BHJ solar cell. Evidence for the model was enhanced by examining the charge carrier behavior and photovoltaic behavior of the integrated devices under illumination of monochromatic light-emitting diodes at different characteristic wavelength. This finding shall pave an interesting possibility for integrated photovoltaic dev...

Shallow acceptor states in Mg-doped CuAlO2 and their effect on structural, electrical, and optical properties are investigated by combining first-principles calculations and experiments. First-principles calculations demonstrate that Mg substituting at the Al site in CuAlO2 plays the role of shallow acceptor and has a low formation energy, suggesting that Mg doping can increase hole concentration and improve the conductivity of CuAlO2. Hall effect measurements indicate that the hole concentration of the Mg-doped CuAlO2 thin film is 2 orders of magnitude higher than that of undoped CuAlO2. The best room temperature conductivity of 8.0 × 10–2 S/cm is obtained. A band gap widening is observed in the optical absorption spectra of Mg-doped CuAlO2, which is well supported by the results from first-principles electronic structure calculations.

In perovskite based planar heterojunction solar cells, the interface between the TiO2 compact layer and the perovskite film is critical for high photovoltaic performance. The deep trap states on the TiO2 surface induce several challenging issues, such as charge recombination loss and poor stability etc. To solve the problems, we synthesized a triblock fullerene derivative (PCBB-2CN-2C8) via rational molecular design for interface engineering in the perovskite solar cells. Modifying the TiO2 surface with the compound significantly improves charge extraction from the perovskite layer. Together with its uplifted surface work function, open circuit voltage and fill factor are dramatically increased from 0.99 to 1.06 V, and from 72.2% to 79.1%, respectively, resulting in 20.7% improvement in power conversion efficiency for the best performing devices. Scrutinizing the electrical properties of this modified interfacial layer strongly suggests that PCBB-2CN-2C8 passivates the TiO2 surface and thus reduces charge recombination loss caused by the deep trap states of TiO2. The passivation effect is further proven by stability testing of the perovskite solar cells with shelf lifetime under ambient conditions improved by a factor of more than 4, from ∼40 h to ∼200 h, using PCBB-2CN-2C8 as the TiO2 modification layer. This work offers not only a promising material for cathode interface engineering, but also provides a viable approach to address the challenges of deep trap states on TiO2 surface in planar perovskite solar cells.

A selenophene-modified PTB7, PBDTSe-TT, is reported. The structure adjustment carried out by alkylselenophene substitution on the BDT building block is shown to slightly affect the polymer’s electronic property, and an enlarged VOC of the resulting photovoltaic device is observed. More importantly, the PBDTSe-TT:PC71BM bulk-heterojunction thin film morphology can be optimized through this modification. As a result, an efficient PCE of 8.8% is achieved without using any solvent additive or special interfacial layer. In addition, the PBDTSe-TT-based device is relatively stable under thermal stress, making it a good candidate for fabricating stacking cells. Finally, a ∼10% PCE tandem device is demonstrated by using identical PBDTSe-TT:PC71BM subcells.

The theory of adenine dimer chain assembly on Cu(110) surface is controversial, due in large to the lack of an adequate description of the van der Waals (vdW) interactions. Here, we show by a combined first-principles calculation and experiment that the role of the vdW interactions is to tilt the energy balance at different levels of chain hierarchy. We find that the stable chains are made of metastable dimers, whereas the metastable chains, close in energy to the stable ones, are made of stable dimers. As such, at room temperate deposition, adenine dimers exist primarily in their stable form. This leads to the formation of metastable chains. By annealing at elevated temperature, however, more dimers can exist in the metastable form. This leads to the nucleation of the stable chains at a different orientation. The thermally controlled chain rotation is expected to be of general importance to the understanding of amino acids assembly and functionalization at the most elemental level.

Silicene, a two-dimensional (2D) honeycomb structure similar to graphene, has been successfully fabricated on an Ir(111) substrate. It is characterized as a (√7×√7) superstructure with respect to the substrate lattice, as revealed by low energy electron diffraction and scanning tunneling microscopy. Such a superstructure coincides with the (√3×√3) superlattice of silicene. First-principles calculations confirm that this is a (√3×√3)silicene/(√7×√7)Ir(111) configuration and that it has a buckled conformation. Importantly, the calculated electron localization function shows that the silicon adlayer on the Ir(111) substrate has 2D continuity. This work provides a method to fabricate high-quality silicene and an explanation for the formation of the buckled silicene sheet.

Seven Zn(II) and Cd(II) coordination polymers, formulated as {[Zn2(5-Br-ip)2(bpy)(H2O)]·2H2O}n (1), {[Zn(5-Br-ip)(bpa)(H2O)]}n (2), {[Cd(5-Br-ip)(bpp)(H2O)]}n (3), {[Zn(5-Br-ip)(bpe)]}n (4), {[Zn2(4-Br-ip)2(bpy)]·H2O}n (5), {[Zn(4-Br-ip)(bpa)(H2O)]}n (6), and {[Cd(4-Br-ip)(bpp)]}n (7), were prepared by hydrothermal reactions based on 4-bromo- or 5-bromoisophthalic acid (4-Br-H2ip or 5-Br-H2ip) and different dipyridyl-type coligands 4,4′-bipyridyl (bpy), 1,2-bi(4-pyridyl)ethane (bpa), 1,3-di(4-pyridyl)propane (bpp), and 1,2-di(4-pyridyl)ethene (bpe). All complexes 1−7 were characterized by elemental analysis, IR spectra, and X-ray single-crystal diffraction. Complex 1 is a 2D (6,3) coordination network and further assembled into a 3D framework via π−π stacking interactions. Complex 2 shows a 1D coordination array and further forms a 2D supramolecular network via H-bonding interactions. Complex 3 has a 2-fold interpenetrating 3D diamond framework. Complex 4 is a 3-fold interpenetrating 3D network with CdSO4...

Eight ZnII and CdII coordination complexes, {[Zn3(nbta)2(bpy)2(H2O)2](H2O)2}n (1), [Zn4(nbta)2(bpe)2(OH)2]n (2), {[Cd3(nbta)2(bpy)5(H2O)2](H2O)6}n (3), {[Cd3(nbta)2(bpe)2(H2O)2](H2O)2}n (4), [Zn2(Hbta)2(bpy)2(H2O)2](H2O) (5), [Zn(bta)(Hbpe)]n (6), [Cd5(bta)2(Hbta)2(bpy)3(H2O)2]n (7), and {[Cd4(bta)2(bpe)2(H2O)4(OH)2](H2O)2}n (8), were prepared via hydrothermal reactions based on H3nbta or H3bta (H3nbta = 5-nitro-1,2,3-benzenetricarboxylic acid and H3bta = 1,2,3-benzenetricarboxylic acid) and the dipyridyl-type coligand 4,4′-bipyridyl (bpy) or 1,2-di(4-pyridyl)ethene (bpe). All complexes were characterized by elemental analysis, IR spectra, and X-ray powder diffraction techniques. Complexes 1−4 all display unusual three-dimensional (3-D) self-penetrating coordination networks. From the topology point of view, complexes 1 and 2 display the 4-connected frameworks with the Schlafli symbols of (4.104.12)2(43.62.8)2(44.62) and (4.62.72.8)2(42.62.7.8), respectively. Complex 3 features an unprecedented 3-nodal ne...