Showing papers by "Donghua University published in 2021"

Single-layered organic photovoltaics with double cascading charge transport pathways: 18% efficiencies

Abstract: The chemical structure of donors and acceptors limit the power conversion efficiencies achievable with active layers of binary donor-acceptor mixtures. Here, using quaternary blends, double cascading energy level alignment in bulk heterojunction organic photovoltaic active layers are realized, enabling efficient carrier splitting and transport. Numerous avenues to optimize light absorption, carrier transport, and charge-transfer state energy levels are opened by the chemical constitution of the components. Record-breaking PCEs of 18.07% are achieved where, by electronic structure and morphology optimization, simultaneous improvements of the open-circuit voltage, short-circuit current and fill factor occur. The donor and acceptor chemical structures afford control over electronic structure and charge-transfer state energy levels, enabling manipulation of hole-transfer rates, carrier transport, and non-radiative recombination losses.

High-entropy ceramics: Present status, challenges, and a look forward

Abstract: High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements. Although in the infant stage, the emerging of this new family of materials has brought new opportunities for material design and property tailoring. Distinct from metals, the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering. Aside from strengthening, hardening, and low thermal conductivity that have already been found in high-entropy alloys, new properties like colossal dielectric constant, super ionic conductivity, severe anisotropic thermal expansion coefficient, strong electromagnetic wave absorption, etc., have been discovered in HECs. As a response to the rapid development in this nascent field, this article gives a comprehensive review on the structure features, theoretical methods for stability and property prediction, processing routes, novel properties, and prospective applications of HECs. The challenges on processing, characterization, and property predictions are also emphasized. Finally, future directions for new material exploration, novel processing, fundamental understanding, in-depth characterization, and database assessments are given.

A Well-Mixed Phase Formed by Two Compatible Non-Fullerene Acceptors Enables Ternary Organic Solar Cells with Efficiency over 18.6%

Abstract: The ternary strategy, introducing a third component into a binary blend, opens a simple and promising avenue to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). The judicious selection of an appropriate third component, without sacrificing the photocurrent and voltage output of the OSC, is of significant importance in ternary devices. Herein, highly efficient OSCs fabricated using a ternary approach are demonstrated, wherein a novel non-fullerene acceptor L8-BO-F is designed and incorporated into the PM6:BTP-eC9 blend. The three components show complementary absorption spectra and cascade energy alignment. L8-BO-F and BTP-eC9 are found to form a homogeneous mixed phase, which improves the molecular packing of both the donor and acceptor materials, and optimizes the ternary blend morphology. Moreover, the addition of L8-BO-F into the binary blend suppresses the non-radiative recombination, thus leading to a reduced voltage loss. Consequently, concurrent increases in open-circuit voltage, short-circuit current, and fill factor are realized, resulting in an unprecedented PCE of 18.66% (certified value of 18.2%), which represents the highest efficiency values reported for both single-junction and tandem OSCs so far.

Approaching 18% efficiency of ternary organic photovoltaics with wide bandgap polymer donor and well compatible Y6 : Y6-1O as acceptor.

Abstract: A series of ternary organic photovoltaics (OPVs) are fabricated with one wide bandgap polymer D18-Cl as donor, and well compatible Y6 and Y6-1O as acceptor. The open-circuit-voltage (VOC ) of ternary OPVs is monotonously increased along with the incorporation of Y6-1O, indicating that the alloy state should be formed between Y6 and Y6-1O due to their excellent compatibility. The energy loss can be minimized by incorporating Y6-1O, leading to the VOC improvement of ternary OPVs. By finely adjusting the Y6-1O content, a power conversion efficiency of 17.91% is achieved in the optimal ternary OPVs with 30 wt% Y6-1O in acceptors, resulting from synchronously improved short-circuit-current density (JSC ) of 25.87 mA cm-2, fill factor (FF) of 76.92% and VOC of 0.900 V in comparison with those of D18-Cl : Y6 binary OPVs. The JSC and FF improvement of ternary OPVs should be ascribed to comprehensively optimal photon harvesting, exciton dissociation and charge transport in ternary active layers. The more efficient charge separation and transport process in ternary active layers can be confirmed by the magneto-photocurrent and impedance spectroscopy experimental results, respectively. This work provides new insight into constructing highly efficient ternary OPVs with well compatible Y6 and its derivative as acceptor.

Underwater Communication and Optical Camouflage Ionogels

Abstract: Marine animals, such as leptocephalus and jellyfish, can sense external stimuli and achieve optical camouflage in the aquatic environment. Fabricating an intelligent soft sensor that can mimic the capabilities of transparent marine animals and function underwater can enable transformative applications in various novel fields. However, previously reported soft sensors struggle to meet the requirements of adhesion, self-healing ability, optical transparency, and stable conductivity in the aquatic environment. Herein, high-performance ionogels by virtue of ion-dipole and ion-ion interactions between fluorine-rich poly(ionic liquid) and ionic liquid are designed. The hydrophobic dynamic viscoelastic networks provide excellent properties for ionogels, including optical transparency, adjustable mechanical properties, underwater self-healing ability, underwater adhesiveness, conductivity, and 3D printability. A mechanically compliant and visually invisible underwater soft sensor based on ionogel is developed. This sensor can achieve optical camouflage, human-body-motion detection, and barrier-free communication in the aquatic environment. A novel contactless sensing mechanism based on changing the electron transfer pathway is proposed. Several interesting functions, such as detection of water environment changes, recognition of objects, delivery of information, and even identification of human standing posture can be realized. Importantly, the ionogel sensor can avoid fatigue and physical damage in the sensing process.

Skin-like mechanoresponsive self-healing ionic elastomer from supramolecular zwitterionic network.

Abstract: Stretchable ionic skins are intriguing in mimicking the versatile sensations of natural skins. However, for their applications in advanced electronics, good elastic recovery, self-healing, and more importantly, skin-like nonlinear mechanoresponse (strain-stiffening) are essential but can be rarely met in one material. Here we demonstrate a robust proton-conductive ionic skin design via introducing an entropy-driven supramolecular zwitterionic reorganizable network to the hydrogen-bonded polycarboxylic acid network. The design allows two dynamic networks with distinct interacting strength to sequentially debond with stretch, and the conflict among elasticity, self-healing, and strain-stiffening can be thus defeated. The representative polyacrylic acid/betaine elastomer exhibits high stretchability (1600% elongation), immense strain-stiffening (24-fold modulus enhancement), ~100% self-healing, excellent elasticity (97.9 ± 1.1% recovery ratio, <14% hysteresis), high transparency (99.7 ± 0.1%), moisture-preserving, anti-freezing (elastic at −40 °C), water reprocessibility, as well as easy-to-peel adhesion. The combined advantages make the present ionic elastomer very promising in wearable iontronic sensors for human-machine interfacing. Ionic skins are of interest for a range of electronic, sensing and interfacing applications but often have trade-offs in properties. Here, the authors report on the creation of a dual network ionic skin using a supramolecular zwitterionic competing network to produce a strain-stiffening, self-healing adhesive sensor.

Large-Area, Flexible, Transparent, and Long-Lived Polymer-Based Phosphorescence Films.

Abstract: Polymer-based room-temperature phosphorescence (RTP) materials with high flexibility and large-area producibility are highly promising for applications in organic electronics. However, achieving such photophysical materials is challenging because of difficulties in populating and stabilizing susceptible triplet excited states at room temperature. Herein large-area, flexible, transparent, and long-lived RTP systems prepared by doping rationally selected organic chromophores in a poly(vinyl alcohol) (PVA) matrix were realized through a hydrogen-bonding and coassembly strategy. In particular, the 3,6-diphenyl-9H-carbazole (DPCz)-doped PVA film shows long-lived phosphorescence emission (up to 2044.86 ms) and a remarkable duration of afterglow (over 20 s) under ambient conditions. Meanwhile, the 7H-dibenzo[c,g]carbazole (DBCz)-doped PVA film exhibits high absolute luminance of 158.4 mcd m2 after the ultraviolet excitation source is removed. The RTP results not only from suppressing the nonradiative decay by abundant hydrogen-bonding interactions in the PVA matrix but also from minimizing the energy gap (ΔEST) between the singlet state and the triplet state through the coassembly effect. On account of the outstanding mechanical properties and the afterglow performance of these RTP materials, they were applied in the fabrication of flexible 3D objects with repeatable folding and curling properties. Importantly, the multichannel afterglow light-emitting diode arrays were established under ambient conditions. The present long-lived phosphorescent systems demonstrate a bright opportunity for the production of large-area, flexible, and transparent emitting materials.

Wearable Thermoelectric Materials and Devices for Self-Powered Electronic Systems.

Abstract: The emergence of artificial intelligence and the Internet of Things has led to a growing demand for wearable and maintenance-free power sources. The continual push toward lower operating voltages and power consumption in modern integrated circuits has made the development of devices powered by body heat finally feasible. In this context, thermoelectric (TE) materials have emerged as promising candidates for the effective conversion of body heat into electricity to power wearable devices without being limited by environmental conditions. Driven by rapid advances in processing technology and the performance of TE materials over the past two decades, wearable thermoelectric generators (WTEGs) have gradually become more flexible and stretchable so that they can be used on complex and dynamic surfaces. In this review, the functional materials, processing techniques, and strategies for the device design of different types of WTEGs are comprehensively covered. Wearable self-powered systems based on WTEGs are summarized, including multi-function TE modules, hybrid energy harvesting, and all-in-one energy devices. Challenges in organic TE materials, interfacial engineering, and assessments of device performance are discussed, and suggestions for future developments in the area are provided. This review will promote the rapid implementation of wearable TE materials and devices in self-powered electronic systems.

Silicate-Enhanced Heterogeneous Flow-Through Electro-Fenton System Using Iron Oxides under Nanoconfinement.

Abstract: Herein, a silicate-enhanced flow-through electro-Fenton system with a nanoconfined catalyst was rationally designed and demonstrated for the highly efficient, rapid, and selective degradation of antibiotic tetracycline. The key active component of this system is the Fe2O3 nanoparticle filled carbon nanotube (Fe2O3-in-CNT) filter. Under an electric field, this composite filter enabled in situ H2O2 generation, which was converted to reactive oxygen species accompanied by the redox cycling of Fe3+/Fe2+. The presence of the silicate electrolyte significantly boosted the H2O2 yield by preventing the O-O bond dissociation of the adsorbed OOH*. Compared with the surface coated Fe2O3 on the CNT (Fe2O3-out-CNT) filter, the Fe2O3-in-CNT filter demonstrated 1.65 times higher kL value toward the degradation of the antibiotic tetracycline. Electron paramagnetic resonance and radical quenching tests synergistically verified that the dominant radical species was the 1O2 or HO· in the confined Fe2O3-in-CNT or unconfined Fe2O3-out-CNT system, respectively. The flow-through configuration offered improved tetracycline degradation kinetics, which was 5.1 times higher (at flow rate of 1.5 mL min-1) than that of a conventional batch reactor. Liquid chromatography-mass spectrometry measurements and theoretical calculations suggested reduced toxicity of fragments of tetracycline formed. This study provides a novel strategy by integrating state-of-the-art material science, Fenton chemistry, and microfiltration technology for environmental remediation.

Direct Magnetic Reinforcement of Electrocatalytic ORR/OER with Electromagnetic Induction of Magnetic Catalysts

Abstract: Designing stable and efficient electrocatalysts for both oxygen reduction and evolution reactions (ORR/OER) at low-cost is challenging. Here, a carbon-based bifunctional catalyst of magnetic catalytic nanocages that can direct enhance the oxygen catalytic activity by simply applying a moderate (350 mT) magnetic field is reported. The catalysts, with high porosity of 90% and conductivity of 905 S m-1 , are created by in situ doping metallic cobalt nanodots (≈10 nm) into macroporous carbon nanofibers with a facile electrospinning method. An external magnetic field makes the cobalt magnetized into nanomagnets with high spin polarization, which promote the adsorption of oxygen-intermediates and electron transfer, significantly improving the catalytic efficiency. Impressively, the half wave-potential is increased by 20 mV for ORR, and the overpotential at 10 mA cm-2 is decreased by 15 mV for OER. Compared with the commercial Pt/C+IrO2 catalysts, the magnetic catalyzed Zn-air batteries deliver 2.5-fold of capacities and exhibit much longer durability over 155 h. The findings point out a very promising strategy of using electromagnetic induction to boost oxygen catalytic activity.

Decomposition of Toluene with a Combined Plasma Photolysis (CPP) Reactor: Influence of UV Irradiation and Byproduct Analysis

Abstract: A combined plasma photolysis (CPP) reactor was used to study the effect of UV irradiation on the removal efficiency and byproducts of toluene decomposition. The influence of UV irradiation length on the removal rate and byproducts were compared. The results show that the toluene removal is obviously improved in the CPP reactor. The removal rate is enhanced with the increase of the UV irradiation length. The increase of removal efficiency is 7.94% and 19.1% under the UV irradiation with 5 cm and 15 cm length, respectively. UV also reduces the production of ozone significantly. It is interesting to find that the effect of UV on the carbon balance is not always increased as expected, but is related to the inlet toluene initial concentration. When the inlet toluene concentration is 300 ppm or 400 ppm, the carbon balance is enhanced by UV. When the inlet concentration is lower, in 60 ppm and 100 ppm, UV no longer plays a positive role. However, UV can change the trend of carbon balance at low initial concentrations and makes it positively related to specific input energy (SIE), which is contrary to the cases without UV.

Location Privacy-preserving Mechanisms in Location-based Services: A Comprehensive Survey

Abstract: Location-based services (LBSs) provide enhanced functionality and convenience of ubiquitous computing, but they open up new vulnerabilities that can be utilized to violate the users’ privacy. The leakage of private location data in the LBS context has drawn significant attention from academics and industry due to its importance, leading to numerous research efforts aiming to confront the related challenges. However, to the best of our knowledge, none of relevant studies have performed a qualitative and quantitative comparison and analysis of the complex topic of designing countermeasures and discussed the viability of their use with different kinds of services and the potential elements that could be deployed to meet new challenges. Accordingly, the purpose of this survey is to examine the privacy-preserving techniques in LBSs. We categorize and provide an inside-out review of the existing techniques. Performing a retrospective analysis of several typical studies in each category, we summarize their basic principles and recent advances. Additionally, we highlight the use of privacy-preserving techniques in LBSs for enabling new research opportunities. Providing an up-to-date and comprehensive overview of existing studies, this survey may further stimulate new research efforts into this promising field.

Residual Chlorine Induced Cationic Active Species on a Porous Copper Electrocatalyst for Highly Stable Electrochemical CO2 Reduction to C2

Abstract: Electrochemical carbon dioxide (CO 2 ) reduction reaction (CO 2 RR) is an attractive approach to deal with the excessive emission of CO 2 and to produce valuable fuels and chemicals in a carbon-neutral way. Many efforts have been devoted to boost the activity and selectivity of high-value multicarbon products (C 2+ ) on Cu-based electrocatalysts. However, Cu-based CO 2 RR electrocatalysts suffer from poor catalytic stability mainly due to the structural degradation and loss of active species under CO 2 RR condition. To date, most reported Cu-based electrocatalysts present stabilities over dozens of hours, which limits the advance of Cu-based electrocatalysts for CO 2 RR. Here, a porous chlorine-doped Cu electrocatalyst is reported and exhibits high C 2+ Faradaic efficiency (FE) of 53.8% at -1.00 V versus reversible hydrogen electrode (V RHE ). Importantly, the catalyst exhibited an outstanding catalytic stability in long-term electrocatalysis over 240 hours. Experimental results show that the chlorine-induced stable cationic Cu 0 -Cu + species and the well-preserved structure with abundant active sites are found to be critical to maintain the high FE of C 2+ in the long-term run of electrochemical CO 2 reduction.

Immunizing Aqueous Zn Batteries against Dendrite Formation and Side Reactions at Various Temperatures via Electrolyte Additives.

Abstract: Aqueous Zn-ion batteries own great potential on next generation wearable batteries due to the high safety and low cost. However, the uncontrollable dendrites growth and the negligible subzero temperature performance impede the batteries practical applications. Herein, it is demonstrated that dimethyl sulfoxide (DMSO) is an effective additive in ZnSO4 electrolyte for side reactions and dendrites suppression by regulating the Zn-ion solvation structure and inducing the Zn2+ to form the more electrochemical stable (002) basal plane, via the higher absorption energy of DMSO with Zn2+ and (002) plane. Moreover, the stable reconstructed hydrogen bonds between DMSO and H2 O dramatically lower the freezing point of the electrolyte, which significantly increases the ionic conductivity and cycling performance of the aqueous batteries at subzero temperatures. As a consequence, the symmetrical Zn/Zn cell can be kept stable for more than 2100 h at 20 °C and 1200 h at -20 °C without dendrite and by-products formation. The Zn/MnO2 batteries can perform steadily for more than 3000 cycles at 20 °C and 300 cycles at -20 °C. This work provides a facile and feasible strategy on designing high performance and dendrite free aqueous Zn-ion batteries for various temperatures.