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1.Visible Light-Induced Degradation of Inverted Polymer:Nonfullerene Acceptor Solar Cells: Initiated by the Light Absorption of ZnO Layer

Author:Liu, BW;Han, YF;Li, ZR;Gu, HM;Yan, LP;Lin, Y;Luo, Q;Yang, SF;Ma, CQ

Source:SOLAR RRL,2021,Vol.5

Abstract:Power conversion efficiencies (PCEs) of polymer solar cells (PSCs) have exceeded 18%% in the last few years. Stability has therefore become the next most important issue before commercialization. Herein, the degradation behaviors of the inverted PM6:IT-4F (PBDB-T-2F:3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2 ',3 '-d ']-s-indaceno[1,2-b:5,6-b ']dithiophene) solar cells with different ZnO layers are systematically investigated. The PCE decay rates of the cells and the photobleaching process of the IT-4F containing organic films on ZnO surface are directly correlated with the light-absorption ability of the ZnO layer in the visible light range, indicating that photochemical decomposition of IT-4F is initiated by the light absorption of ZnO layer. By analyzing the products of the aged ZnO/IT-4F films with matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), it is confirmed that photochemical reactions at the IT-4F/ZnO interface include de-electron-withdrawing units and dealkylation on the side-phenyl ring. Hydroxyl radicals generated by the photo-oxidation of dangling hydroxide by ZnO are confirmed by electron spin resonance (ESR) spectroscopy measurements, which is attributed as the main reason causing the decomposition of IT-4F. Surface treatment of ZnO with hydroxide and/or hydroxyl radical scavenger is found to be able to improve the stability of the PSCs, which further supports the proposed degradation mechanism.

2.Electrochemical gating for single-molecule electronics with hybrid Au|graphene contacts

Author:Tao,Shuhui;Zhang,Qian;Vezzoli,Andrea;Zhao,Cezhou;Zhao,Chun;Higgins,Simon J.;Smogunov,Alexander;Dappe,Yannick J.;Nichols,Richard J.;Yang,Li

Source:Physical Chemistry Chemical Physics,2022,Vol.24

Abstract:The single-molecular conductance of a redox active viologen molecular bridge between Au|graphene electrodes has been studied in an electrochemical gating configuration in an ionic liquid medium. A clear “off-on-off” conductance switching behaviour has been achieved through gating of the redox state when the electrochemical potential is swept. The Au|viologen|graphene junctions show single-molecule conductance maxima centred close to the equilibrium redox potentials for both reduction steps. The peak conductance of Au|viologen|graphene junctions during the first reduction is significantly higher than that of previously measured Au|viologen|Au junctions. This shows that even though the central viologen moiety is not directly linked to the enclosing electrodes, substituting one gold contact for a graphene one nevertheless has a significant impact on junction conductance values. The experimental data was compared against two theoretical models, namely a phase coherent tunnelling and an incoherent “hopping” model. The former is a simple gating monoelectronic model within density functional theory (DFT) which discloses the charge state evolution of the molecule with electrode potential. The latter model is the collective Kuznetsov Ulstrup model for 2-step sequential charge transport through the redox centre in the adiabatic limit. The comparison of both models to the experimental data is discussed for the first time. This work opens perspectives for graphene-based molecular transistors with more effective gating and fundamental understanding of electrochemical electron transfer at the single molecular level.

3.In Silico Tuning of the Pore Surface Functionality in Al-MOFs for Trace CH3I Capture

Author:Wu, XY;Chen, LJ;Amigues, EJ;Wang, RY;Pang, ZF;Ding, LF

Source:ACS OMEGA,2021,Vol.6

Abstract:Aluminum (Al)-based metal-organic frameworks (MOFs) have been shown to have good stability toward. irradiation, making them promising candidates for durable adsorbents for capturing volatile radioactive nuclides. In this work, we studied a series of existing Al-MOFs to capture trace radioactive organic iodide (ROI) from a gas composition (100 ppm CH3I, 400 ppm CO2, 21%% O-2, and 78%% N-2) resembling the off-gas composition from reprocessing the used nuclear fuel using Grand canonical Monte Carlo (GCMC) simulations and density functional theory (DFT) calculations. Based on the results and understanding established from studying the existing Al-MOFs, we proceed by functionalizing the top-performing CAU-11 with different functional groups to propose better MOFs for ROI capture. Our study suggests that extraordinary ROI adsorption and separation capability could be realized by -SO3H functionalization in CAU-11. It was mainly owing to the joint effect of the enhanced pore surface polarity arising from -SO3H functionalization and the mu-OH group of CAU-11.

4.First-principles materials simulation and design for alkali and alkaline metal ion batteries accelerated by machine learning

Author:Jin, LJ;Ji, YJ;Wang, HS;Ding, LF;Li, YY


Abstract:The challenge of regeneration of batteries requires a performance improvement in the alkali/alkaline metal ion battery (AMIB) materials, whereas the traditional research paradigm fully based on experiments and theoretical simulations needs massive research and development investment. During the last decade, machine learning (ML) has made breakthroughs in many complex disciplines, which testifies to their high processing speed and ability to capture relationships. Inspired by these achievements, ML has also been introduced to bring a new paradigm for shortening the development of AMIB materials. In this Perspective, the focus will be on how this new ML technology solves the key problems of redox potentials, ionic conductivity and stability parameters in first-principles materials' simulation and design for AMIBs. It is found that ML not only accelerates the property prediction, but also gives physicochemical insights into AMIB materials' design. In addition, the final part of this paper summarizes current achievements and looks forward to the progress of a novel paradigm in direct/inverse design with the increasing number of databases, skills, and ML technologies for AMIBs.

5.Asymmetric Effect on the Length Dependence of Oligo(Phenylene ethynylene)-Based Molecular Junctions

Author:Fan,Yinqi;Pitie,Sylvain;Liu,Chenguang;Zhao,Cezhou;Zhao,Chun;Seydou,Mahamadou;Dappe,Yannick J.;Nichols,Richard J.;Yang,Li

Source:Journal of Physical Chemistry C,2021,Vol.126

Abstract:It is well known that the electrical conductance of molecular junctions in the tunneling regime varies exponentially with the length of the molecular backbone. This behavior is strongly influenced by anchoring groups, which connect the molecular backbone to the electrodes and locate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) resonances with respect to the Fermi level. Nevertheless, most of the studies have been performed on symmetric junctions, namely, using the same electrodes and anchoring groups at both sides of the junctions. Only recently, there have been some reports detailing the influence of introducing asymmetry into single-molecule junctions, using different contacts or different anchoring groups at either end of the molecular bridge. These studies have revealed that such junction asymmetry strongly impacts electrical characteristics. In this study, Au and graphene electrodes were used to provide asymmetry to a single-molecule junction. The conductance and length dependence of amine and methyl sulfide-terminated oligo(phenylene ethynylene) have been determined experimentally and theoretically. The impact of introducing this asymmetry has been quantified by comparing the conductance and β values of oligo(phenylene ethynylene) (OPE)-based molecules within Au/Au electrodes and Au/graphene junctions, respectively. Our results show that the introduction of a graphene electrode leads to lower conductance values and attenuation factors, similar to what has been previously observed in alkane chains. This is attributed to a shift of the electronic molecular levels toward the Fermi level, mainly driven by acetylene groups linking adjacent phenyl groups.

6.Improved pseudocapacitances of supercapacitors based on electrodes of nitrogen-doped Ti3C2Tx nanosheets with in-situ growth of carbon nanotubes

Author:Sun, Y;Yi, RW;Zhao, YC;Liu, CG;Yuan, YD;Geng, XW;Li, WX;Feng, ZC;Mitrovic, I;Yang, L;Zhao, CZ


Abstract:A facile strategy involving only liquid mixing, drying, and annealing processes has been designed to fabricate a new MXene-based material containing nitrogen-doped carbon nanotubes grown on the nitrogen-modified titanium carbides (NCMX). During the thermal treatment, the nitrogen doping is dually achieved in MXene nanosheets and carbon nanotubes while the in-situ growth of carbon nanotubes occurs. The NCMX electrode exhibits the well-designed structure with the promoted specific surface area and specific capacitance. More attractively, the resultant NCMX-4 material shows extraordinary improved electrochemical capacitances of 299.52 F g(-1) at the scan rate of 2 mV s(-1) in the 3 M H2SO4 electrolyte, which is remarkably more superior than those of the pure un-doped one (74.98 F g(-1)). It delivers an excellent capacitance retention capability of 84.2%% after 10,000 cycles. Our results highlight that the strategy of fabricating novel NCMX materials here can be readily applied to a large industrial scale for improving the pseudocapacitance of supercapacitors. (C) 2020 Elsevier B.V. All rights reserved.

7.A high conductive TiC-TiO2/SWCNT/S composite with effective polysulfides adsorption for high performance Li-S batteries

Author:Geng, XW;Yi, RW;Lin, XF;Liu, CG;Sun, Y;Zhao, YC;Li, YQ;Mitrovic, I;Liu, R;Yang, L;Zhao, CZ


Abstract:Lithium-sulfur (Li-S) batteries have attracted more and more attention in recent years, as their theoretical capacity is several times larger than conventional lithium-ion batteries and they have a high energy density in secondary battery systems. In our work, a titanium carbide - titanium dioxide/single-walled carbon nanotube/sulfur (TiC-TiO2/SWCNT/S) cathode with high conductivity and effective polysulfides adsorption is prepared by a facile method for fabricating Li-S batteries. The batteries with this composite cathode show a good performance at 0.1 C due to relatively high utilization of sulfur, reaching 1338.6 mAh.g(-1) specific capacity at first cycle and retaining 802.5 mAh.g(-1) after 100 cycles. Meanwhile, it presents an excellent rate performance with 711.2 mAh.g(-1) at 4 C, and recovers to 1006.9 mAh.g(-1) when the current returns to 0.1 C. Also a slow capacity decay (0.045%% decay rate per cycle) is observed at 1 C. These results suggest that a small amount of SWCNT can increase the conductivity of the whole composite to a great extent, and the strong adsorption ability of TiO2 increases the cycle life. This work offers an efficient and low-cost strategy to obtain high performance batteries with great potential for commercial applications. (C) 2020 Elsevier B.V. All rights reserved.

8.Crystal Engineering through Multiple Intermolecular Interactions:from(H2bipy)[Cu(ox)2] to(H2bipy)(ADC)(bipy = 4,4'-bipyridine; ox = oxalate; ADC = acetylenedicarboxylate)



Abstract:  本文利用分子间作用力合成了四个化学组成截然不同,但晶体结构同构的的化合物,(H2bipy)[Cu(ox)2](1),(H2bipy)[NaH(ox)2](2),(H2bipy)[H2(ox)2](3)和(H2bipy)(ADC)(4),测定并研究了其超分子结构,指出三种分子间力,N-H…O,C-H…O 和π-π的存在是导致四个晶体同构的根本原因。

9.Oligothiophene molecular wires at graphene-based molecular junctions

Author:Gao, Tingwei ; He, Chunhui ; Liu, Chenguang ; Fan, Yinqi ; Zhao, Cezhou ; Zhao, Chun ; Su, Weitao ; Dappe, Yannick J. ; Yang, Li

Source:Physical Chemistry Chemical Physics,2021,Vol.23

The use of graphene as a new type of electrode at molecular junctions has led to a renewal of molecular electronics. Indeed, the symmetry breaking induced by the graphene electrode yields different electronic behaviors at the molecular junction and in particular enhanced conductance for longer molecules. In this respect, several studies involving different molecular backbones and anchoring groups have been performed. Here in the same line, we consider oligopthiophene based hybrid gold-graphene junctions and we measure their electrical properties using the STM-I(s) method in order to determine their attenuation factor and the effect of specific anchoring groups. The results are supported by density functional theory (DFT) calculations, and exhibit a similar behavior to what is observed at alkane-based junctions.
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10.Cyclopentadithiophene cored A-pi-D-pi-A non-fullerene electron acceptor in ternary polymer solar cells to extend the light absorption up to 900 nm

Author:Zhang, YX;Liu, XC;Gu, HM;Yan, LP;Tan, HW;Ma, CQ;Lin, Y


Abstract:Conjugated small molecular non-fullerene electron acceptors (NFA) are considered as one of the critical materials for achieving high performance and low cost of polymer solar cells, and received much attention in the last few years. However, most of the NFAs are based on large fused ic-aromatic core, which requires complicate synthesis efforts. In addition, the relatively weak light absorption limited to 800 nm of most the NAFs limits the energy harvesting capability of the solar cells. In this paper, we report an A-pi-D-pi-A type molecule cored with a cyclopentadithiophene unit, which can be easily synthesized in two steps from commercially available starting materials. This compound shows a broad absorption up to 900 nm in thin solid film, which is ascribed to the relatively high highest occupied molecular orbital (HOMO) energy level as confirmed by cyclic voltammery and theoratical calculation. Application of the compound in polymer solar cells was also investigated both in binary and in ternary systems. The optimized power conversion efficiency (PCE) in binary solar cell with PTB7-Th as donor is 5.76%% with an open circuit voltage (V-OC) of 0.838 V, a short circuit current (J(SC)) of 14.81 mA/cm(2) and a fill factor (FF) of 46.4%%. In the ternary solar cells which includes a second acceptor, PC71BM, the highest PCE achieved is 9.39%% with a V-OC of 0.803 V, a J(SC) of 19.01 mA/cm (2), a FF of 61.6%%, which is over 20%% enhancement compared to the PTB7-Th:PC71BM system (PCE of 7.58%%). This work develops a simple small molecule nonfullerene acceptor which can largely enhance the photo response in near infrared region to improve the performance of fullerene based organic solar cell.

11.Ruthenium single-atom catalysis for electrocatalytic nitrogen reduction unveiled by grand canonical density functional theory

Author:Ji, YJ;Li, YF;Dong, HL;Ding, LF;Li, YY


Abstract:To substitute the intensive energy-consuming Haber-Bosch process for the industrial production of ammonia, the theoretical exploration of catalysts for electrocatalytic nitrogen reduction reaction (eNRR) into ammonia is critical to obtain an insightful mechanism and principles for designing electrocatalysts. However, most studies adopted the constant charge model (CCM), although an electrochemical system corresponds to the constant potential model (CPM) in reality. Herein, considering the benchmark of carbon-supported Ru single atom catalysts, we systematically examined the adsorption of eNRR intermediates under the condition of constant electrode potential to obtain the eNRR mechanism and optimal active site based on the grand canonical density functional theory (GC-DFT). The comparison study demonstrated that, during the electrochemical processes, the inherent electrons exchanged, ignored by the CCM, play an important role in the quantitative determination of Gibbs free energy change, particularly at the potential-determining step, leading to the conclusion that the RuN(4)motif has a lower limiting potential (-0.66 V) than the RuN(3)motif (-1.22 V) in the CPM. Importantly, Ru, a single atom bonded with two carbon atoms and two nitrogen atoms, is identified as the optimal eNRR reaction site with the lowest limiting potential of -0.43 V. This work both accurately describes the practical eNRR process for Ru-based single-atom catalysts from the prospective of electrocatalysis and improves the identification protocol for the theoretical exploration and design of electrocatalysts.

12.High-performance solution-processed Ti3C2Tx MXene doped ZnSnO thin-film transistors via the formation of a two-dimensional electron gas

Author:Zhao, TS;Liu, CG;Zhao, C;Xu, WY;Liu, YN;Mitrovic, IZ;Lim, EG;Yang, L;Zhao, CZ


Abstract:MXenes are a large class of two-dimensional (2D) materials widely studied recently since they have good water solubility and are able to tune the work function (WF) of materials without changing their electronic characteristics. Based on this, aqueous solution-processed indium-free zinc tin oxide (ZTO) thin-film transistors (TFTs) have been fabricated under an annealing temperature of 300 degrees C and successfully optimized. This optimization is achieved by fabricating a channel layer into a homojunction structure (MXene doped ZTO/ZTO) to form a two-dimensional electron gas (2DEG). Through doping the specific concentrations of Ti3C2Tx MXenes into the upper layer ZTO thin films, the TFTs exhibit enhanced field-effect mobilities (mu(FE)) of 10.77 cm(2) V-1 s(-1) and 13.06 cm(2) V-1 s(-1) as well as a large on/off current ratio of more than 10(8). Moreover, compared with the undoped double-layer ZTO TFTs, the homojunction devices show better stability, mainly resulting from the transformation in leading conduction mode. Finally, through applying the homojunction channel on the solution-processed aluminum oxide (AlOx) dielectric layer, the mu(FE) exhibits a further enhanced value of 28.35 cm(2) V-1 s(-1). This is the first report to apply MXenes to the channel layer of TFTs and to fabricate solution-processed ZTO thin films via an aqueous solvent under 300 degrees C.

13.Optimizing the Electrochemiluminescence of Readily Accessible Pyrido[1,2-alpha]pyrimidines through "Green" Substituent Regulation

Author:Zhang, RZ;Cheng, J;Yang, LQ;Wong, JM;Adsetts, JR;Wang, RY;Liu, JY;Ding, ZF;Wang, HB


Abstract:Bright and low-cost emitting organic molecules are very desirable for electrochemiluminescence (ECL). Here, we report a facile one-step, three-component reaction of readily available precursors to synthesize pyrido[1,2-alpha]pyrimidine derivatives (1-4), all which give off green photoluminescence (PL). In contrast, the electrochemistry and ECL properties of these luminophores are affected by the extent of the conjugation and the nature of the peripheral substituents. Density functional theory (DFT) calculations identified the aromatic chain substitution could extend the conjugation of pyrido[1,2-alpha]pyrimidine core and stabilize the electrogenerated radicals required for generation of an excited state, affording pyrido[1,2-alpha]pyrimidine 3 the highest ECL activity among the studied samples. ECL in annihilation route confirmed weak emission, but great improvement was made using oxidizing co-reactant species (benzoate radical from benzoyl peroxide, BPO) with an efficiency of 43 %% relative to that of Ru(bpy)(3)(PF6)(2). The pyrido[1,2-alpha]pyrimidine 3/BPO system is more robust than those of reducing co-reactant species [tri-n-propylamine radical or 2-(dibutylamino) ethanol radical] and is one of the highest among the reported organic electrochemiluminophores. ECL spectroscopy revealed that the monomeric excited states were the main species to emit light. Their straightforward, one-step, green synthesis, and their structure tunability represent significant advantages in the development of readily accessible dyes for PL and especially ECL applications.

14.A Ti3C2Tx MXene-carbon nanocage-sulfur cathode with high conductivity for improving the performance of Li-S batteries

Author:Geng, XW;Liu, CG;Sun, Y;Zhao, YC;Yi, RW;Song, PF;Zhao, C;Mitrovic, I;Yang, L;Zhao, CZ


Abstract:Lithium-sulfur (Li-S) batteries hold their promise in renewable next-generation energy storage technologies due to low cost and high theoretical energy. Herein, a Ti3C2Tx MXene-carbon nanocage-sulfur (MXene/CNC/S) cathode is synthesized by a simple process with high conductivity and outstanding performance in Li-S batteries. The cathode with an unusually high sulfur content of 80%% demonstrates an eminent initial specific capacity of 1275.5 mAh.g(-1) at 0.1 degrees C and retains 823.8 mAh.g(-1) after 100 cycles, showing a high retention rate of 64.6%%. Besides, it exhibits a great conductive feature for rate performance, delivering 630.5 mAh.g(-1) capacity when the current rises to 4 degrees C. In this composition electrode, the excellent electrochemical performance indicates that MXene can effectively adsorb polysulfides to help batteries achieve long-term cyclic performance. On the other hand, the introduction of CNC strongly improves the specific surface area of the cathode and constructs a high conductive network to reduce the stacking of MXene, thus exhibiting better rate performance and increasing utilization of sulfur. Our work holds future technological significance as it could accelerate progress towards lithium-sulfur batteries with high sulfur content and less pricy conductive materials. (C) 2021 Elsevier B.V. All rights reserved.

15.CaO catalyst for multi-route conversion of oakwood biomass to value-added chemicals and fuel precursors in fast pyrolysis

Author:Gupta, Jyoti ; Papadikis, Konstantinos ; Konysheva, Elena Yu. ; Lin, Yi ; Kozhevnikov, Ivan V. ; Li, Jingjing

Source:Applied Catalysis B Environmental,2021,Vol.285

Abstract:The impact of CaO on oakwood pyrolysis was explored by the Py-GC/MS at 500 °C. Ca(OH)2 presents on the CaO surface, indicating its partial hydration (noted as CaOOH). CaOOH promoted the ketonisation of carboxylic acids to aliphatic ketones, furfural to cyclopentanone/2-cyclopentenone, facilitated the elimination of the methoxy-phenolic compounds. The catalyst loading did not show any significant effect on the formation of acetone, while a noticeable reduction in the phenolics was revealed. Increasing catalyst loading almost eliminated CO2, acids, furans, aldehydes, ether groups, whilst the fractions of alcohols, esters, sugars, and alkoxybenzene decreased noticeably. The use of partially hydrated CaOOH in the CFP can create conditions where by-products generated during the ketonisation and phenolics upgrading reactions (CO2, H2O, CO) interact through the adsorption enhance water-gas-shift reaction and through coking reactions with formation of H2 used for hydrogenation during multistep conversion of furfural to cyclopentanone in a vapour phase. © 2020 Elsevier B.V.

16.Advances of RRAM Devices: Resistive Switching Mechanisms, Materials and Bionic Synaptic Application

Author:Shen, ZJ;Zhao, C;Qi, YF;Xu, WY;Liu, YN;Mitrovic, IZ;Yang, L;Zhao, CZ


Abstract:Resistive random access memory (RRAM) devices are receiving increasing extensive attention due to their enhanced properties such as fast operation speed, simple device structure, low power consumption, good scalability potential and so on, and are currently considered to be one of the next-generation alternatives to traditional memory. In this review, an overview of RRAM devices is demonstrated in terms of thin film materials investigation on electrode and function layer, switching mechanisms and artificial intelligence applications. Compared with the well-developed application of inorganic thin film materials (oxides, solid electrolyte and two-dimensional (2D) materials) in RRAM devices, organic thin film materials (biological and polymer materials) application is considered to be the candidate with significant potential. The performance of RRAM devices is closely related to the investigation of switching mechanisms in this review, including thermal-chemical mechanism (TCM), valance change mechanism (VCM) and electrochemical metallization (ECM). Finally, the bionic synaptic application of RRAM devices is under intensive consideration, its main characteristics such as potentiation/depression response, short-/long-term plasticity (STP/LTP), transition from short-term memory to long-term memory (STM to LTM) and spike-time-dependent plasticity (STDP) reveal the great potential of RRAM devices in the field of neuromorphic application.

17.Simultaneously Achieving Highly Efficient and Stable Polymer:Non-Fullerene Solar Cells Enabled By Molecular Structure Optimization and Surface Passivation

Author:Liu, BW;Su, X;Lin, Y;Li, ZR;Yan, LP;Han, YF;Luo, Q;Fang, J;Yang, SF;Tan, HW;Ma, CQ

Source:ADVANCED SCIENCE,2022,Vol.9

Abstract:Despite the tremendous efforts in developing non-fullerene acceptor (NFA) for polymer solar cells (PSCs), only few researches are done on studying the NFA molecular structure dependent stability of PSCs, and long-term stable PSCs are only reported for the cells with low efficiency. Herein, the authors compare the stability of inverted PM6:NFA solar cells using ITIC, IT-4F, Y6, and N3 as the NFA, and a decay rate order of IT-4F > Y6 approximate to N3 > ITIC is measured. Quantum chemical calculations reveal that fluorine substitution weakens the CC bond and enhances the interaction between NFA and ZnO, whereas the beta-alkyl chains on the thiophene unit next to the CC linker blocks the attacking of hydroxyl radicals onto the CC bonds. Knowing this, the authors choose a bulky alkyl side chain containing molecule (named L8-BO) as the acceptor, which shows slower photo bleaching and performance decay rates. A combination of ZnO surface passivation with phenylethanethiol (PET) yields a high efficiency of 17%% and an estimated long T-80 and Ts-80 of 5140 and 6170 h, respectively. The results indicate functionalization of the beta-position of the thiophene unit is an effective way to improve device stability of the NFA.
Total 17 results found
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