Structural,electronic,and Li-ion mobility properties of garnet-type Li_(7)La_(3)Zr_(2)O_(12) surface:An insight from first-principles calculations

Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) is a promising solid-state electrolyte for Li-ion batteries,but Li-dendrite's formation greatly limits the applications.In this paper,we systematically investigate the stability,electronic properties,and Li-ion mobility of the LLZO surface by the ifrst-principles calculations.We consider the(110) and(001) slab structures with different terminations in the t-and c-LLZO.Our results indicate that both(110) and(001) surfaces prefer to form Li-rich termination due to their low surface energies for either t-or c-LLZO.Moreover,with the decrease of Li contents the stability of Li-rich surfaces is improved initially and degrades later.Unfortunately,the localized surface states at the Fermi level can induce the formation of metallic Li on the Li-rich surfaces.In comparison,Li/La-termination has a relatively low metallic Li formation tendency due to its rather low diffusion barrier.In fact,Li-ion can spontaneously migrate along path II(Li3→Li2) on the Li/La-T(001) surface.In contrast,it is more difficult for Li-ion diffusion on the Li-T(001) surface,which has a minimum diffusion barrier of 0.50 eV.Interestingly,the minimum diffusion barrier decreases to 0.34 eV when removing four Li-ions from the Li-T(001) surface.Thus,our study suggests that by varying Li contents,the stability and Li-ion diffusion barrier of LLZO surfaces can be altered favorably.These advantages can inhibit the formation of metallic Li on the LLZO surfaces.

Realizing high-performance organic solar cells through precise control of HOMO driving force based on ternary alloy strategy

A good deal of studies have proven that effective exciton dissociation and fast hole transport can operate efficiently in non-fullerene organic photovoltaics(OPVs)despite nearly zero driving force.Even so,whether such a phenomenon is universal and how small the driving force can realize the best photovoltaic performance still require a thorough understanding.Herein,despite the zero driving force based on PM6:F8IC system,a maximum short-circuit current(J_(sc))of 23.0 mA/cm^(2) and high power conversion efficiency(PCE)of 12.2%can still be achieved.Due to the continuously adjustable energy levels can be realized in organic semiconducting alloys including F8IC:IT-4F and F8IC:Y6,the suitable third components can play the role of energy level regulator.Therefore,the HOMO energy level offset(DEHOMO(D A))from zero to 0.07 and 0.06 eV is accomplished in the optimized IT-4F and Y6 ternary devices.Consequently,both ternary devices achieved substantially increased PCE of 13.8%and Jsc of 24.4 and 25.2 mA/cm^(2),respectively.Besides,pseudo-planar heterojunction(PPHJ)devices based on alloyed acceptors through sequential spin-coating method further improve the photovoltaic performance.Our work puts forward the concept of energy level regulator and prove that the ternary alloy strategy has unique advantages and huge research potential in continuously adjusting the driving force.

Non-conjugated terpolymer acceptors for highly efficient and stable lager-area all-polymer solar cells

All-polymer solar cells(all-PSCs)have made significant progress recently,but few studies have been conducted to investigate the lab-to-manufacturing translation from the spin-coating method to the printing process.Here,the random copolymerization method and non-conjugated backbone approach are integrated to manipulate the morphology and photoelectric properties of the active layer for large-area printed all-PSCs.A series of non-conjugated terpolymer acceptors PYSe-TC_(6)T(x)(x=5,10,and 20,refers to the molar ratio of TC_(6)T unit)are developed by covalently introducing non-conjugated unit TC_(6)T into the PYSe host bipolymer by random copolymerization.The spin-coated PYSe-TC_(6)T(10)-based all-PSC demonstrates the best power conversion efficiency(PCE)of 13.54%,superior to the PYSe-based one(12.45%).More intriguingly,morphological studies reveal that a combination of the random polymerization and non-conjugated backbone strategy can effectively prevent the active layer from overaggregation and improve the film quality during the printing process,thereby minimizing the efficiency and technology gap between spin-coated small-area devices and blade-coated large-area devices.By directly using the same preparation condition of spin-coating,the blade-coated small-area(0.04 cm^(2))delivers a PCE of 12.83%and the large-area(1.21 cm^(2))device achieves a PCE of 11.96%with a small PCE loss.Both PCE value and PCE loss are one of the most outstanding performances of the bladecoated all-PSCs.These findings reveal that a combination of the non-conjugated flexible backbone with random copolymerization to develop non-conjugated terpolymers is an attractive design concept to smoothly realize the lab-to-manufacturing translation.

Decrypting the Influence of Axial Coordination on the Electronic Microenvironment of Co-N_(5)Site for Enhanced Electrocatalytic Reaction

Metal porphyrins are star molecules that possess welldefined coordination metal centers for versatile catalytic reactions.However,most previous work has focused on the correlations between in-plane symmetric configuration of metal-N_(4)sites and their catalytic performance.Addressing the catalytic contribution of additional axial coordination to such symmetric configuration remains a challenge.Theoretical calculations revealed that axially anchoring an extra pyridine on the tetra-coordinated cobalt porphyrin(Co-N4)to construct penta-coordinated cobalt porphyrin(Co-N_(5))renders cobalt a higher electron density,thereby favoring the rate-determining O_(2)adsorption/activation and reducing the oxygen electroreduction barrier.Therefore,a well-defined Co-N_(5)site is rationally introduced into the azo-linked polymer framework for a fundamental structure-catalytic performance correlation study.As-prepared Co-N_(5)catalyst exhibits a 26 mV positive shift in half-wave potential compared with the pyridine-free Co-N_(4)counterpart,discloses a markedly higher power density(141.4 mW cm^(−2)),and possesses better long-term durability(over 160 h cycles)in a Zn-air battery.Moreover,such a Co-N_(5)catalyst also showcases potential applications for CO_(2)reduction with high CO_(2)-to-CO conversion faradic efficiency and better selectivity than the Co-N_(4)counterpart because coordination of the fifth pyridine evokes electronic localization that suppresses a competitive side reaction.This work proves the positive electrocatalytic contribution of axial penta-coordination on well-defined metalporphyrin-based catalysts and offers atomic understanding of the structure-performance correlation on single atom catalysts for future catalyst design.

A generalized one-step in situ formation of metal sulfide/reduced graphene oxide nanosheets toward high-performance supercapacitors

Metal sulfides are promising candidates for supercapacitors,but their slow reaction kinetics hinders their electrochemical performance.Large electrochemical surface area and combination with conductive carbon are potential methods to improve their capacitive performance.However,seeking for a generalized and simple approach to prepare two-dimensional composites of metal sulfide and conductive carbon for supercapacitors is challengeable.Herein,a generalized and facile one-step pyrolysis method was designed for in situ growth of cobalt nickel sulfides(CoNi2S4)on reduced graphene oxide(rGO)nanosheets(CoNi2S4/rGO)under mild conditions.The as-prepared CoNi2S4/rGO materials possess the nanoparticles-on-nanosheets structure,which is effective to provide a myriad of active sites and optimized electron/ion diffusion pathway.Benefiting from those advantages,the resultant CoNi2S4/rGO electrodes exhibit impressed specific capacitances of 1526 and 988 F g^−1 at 2 and 20 A g^−1,respectively.The supercapacitors based on CoNi2S4/rGO showcase an operation potential window of 1.6 V,and energy density of 54.8 W h kg^−1 at the power density of 798 W kg^−1.The capacitance retention of the supercapacitor is about 93.7%after 8000 cycles at 3 A g^−1.Moreover,a series of metal sulfide/rGO hybrids are obtained by this generalized strategy,which could be extended to construct electrode materials for various energy devices.

Enabling 2.4-V aqueous supercapacitors through the rational design of an integrated electrode of hollow vanadium trioxide/carbon nanospheres

Aqueous supercapacitors(SCs)exhibit several advantages,including high-power density,cycling durability,and safety;however,the shortage of low energy density inhibits their further application.Acquiring an excellent performance upon using simple strategies would be beneficial,but remains challenging.Here,an integrated electrode of hollow V_(2)O_(3)/carbon nanospheres(H-V_(2)O_(3)/C)was designed and synthesized for SCs.The introduction of carbon can increase the conductivity and stability,whereas the hollow structure endows H-V_(2)O_(3)/C with a high specific surface area and rapid transport of ions.Moreover,the H-V_(2)O_(3)/C integrated electrode can simultaneously work in both negative and positive potential windows.Benefiting from these advantages,the H-V_(2)O_(3)/C integrated electrode exhibits a specific capacitance as high as 708.6 F g^(-1) in a wide voltage window of-1.1-1.3 V.Furthermore,stemming from the multiple energy storage mechanisms,the aqueous integrated full SC device exhibits a wider potential window and higher energy density than the traditional(a)symmetric ones.Therefore,the proposed device delivers a wide voltage window of 2.4 V with an energy density of 96.8 W h kg^(-1) at a power density of 1204.6 W kg^(-1),as well as superior cycling stability.This study enlightens the design and preparation of electrode materials,opening up a possible approach for developing wide-voltage aqueous SCs.

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet–Triplet Annihilation Upconversion Perovskite Solar Cells

The novel triplet–triplet annihilation(TTA)upconversion(UC)field of rubrene(Rub)and dibenzotetraphenylperiflanthene(DBP)sensitized by bulk metal halide perovskite,integrated with copper-2,3,9,10,16,17,23,24-octafluorophthalocyanine(F_(8)CuPc)as cosensitizer,have been investigated in perovskite solar cells(PVSCs)to minimize sub-bandgap photon transmission loss.The firm hydrogen bonding interaction(F…H–N between F_(8)CuPc and MA+),cation-πinteraction(MA+with Rub),and the hydrophobic characteristic of additives enable F_(8)CuPc:Rub:DBP dually-sensitized p-i-n PVSCs based on MAPbI_(3)and Cs_(0.05)(FA_(0.83)MA_(0.17))_(0.95)Pb(Br_(0.17)I_(0.83))_(3)absorbers to attain champion efficiencies of 20.83%and 21.51%,respectively.Furthermore,due to the excellent photochemical and thermal stability of F_(8)CuPc,the corresponding PVSCs can maintain nearly 80%of the original efficiencies exposed to air with 50∼70%relative humidity over 1100 h and N_(2)at 85℃for 300 h.

Cementitious grain-boundary passivation for flexible perovskite solar cells with superior environmental stability and mechanical robustness

The power conversion effciency(PCE)of flexible perovskite solar cells(PSCs)has increased rapidly,while the mechanical flexibility and environmental stability are still far from satisfactory.Previous studies show the environmental degradation and ductile cracks of perovskite films usually begin at the grain boundaries(GBs).Herein,sulfonated graphene oxide(s-GO)is employed to construct a cementitious GBs by interacting with the[Pb I6]4–at GBs.The resultant s-GO-[Pb I6]4–complex can effectively passivate the defects of vacant iodine,and the devices with s-GO exhibit remarkable waterproofness and flexibility due to the tough and water-insoluble GBs.The champion PCE of 20.56%(1.01 cm^(2))in a device treated with s-GO is achieved.This device retains 90%of its original PCE after 180 d stored in the ambient condition,as well as over 80%retention after 10,000 bending cycles at a curvature radius of 3 mm.

Printable and stable all-polymer solar cells based on non-conjugated polymer acceptors with excellent mechanical robustness

All-polymer solar cells(all-PSCs)trigger enormous commercial applications,and great progress has been made in recent years.However,from small-area devices to large-area modules,the poor adaption of the materials for printing methods and the large efficiency loss are still great challenges.Herein,three novel non-conjugated polymer acceptors(PTH-Y,PTClm-Yand PTClo-Y)are developed for all-PSCs.It can be found that non-conjugated polymer acceptors can effectively minimize the technique and efficiency gaps between small-area spin-coating and large-area blade-printing method,which can facilitate the preparation of large-area flexible device.By directly inheriting the spin-coating condition,the blade-coating processed device based on PTCloY achieves an impressive power conversion efficiency(PCE)of 12.42%,comparable to the spin-coating processed one(12.74%).Such a non-conjugated polymer system also can well tolerate large-scale preparation and flexible substrate.Notable PCE of 11.94%for large-area rigid device and 11.56%for large-area flexible device are obtained,which is the highest value for large-area flexible all-PSCs fabricated by blade-coating.In addition,the non-conjugated PTClo-Y-based devices show excellent thermal stability and mechanical robustness.These results demonstrate that the non-conjugated polymer acceptors are potential candidates for the fabrication of highly-efficient,large-area and robust flexible all-PSCs by printing methods.

A non-wetting and conductive polyethylene dioxothiophene hole transport layer for scalable and flexible perovskite solar cells

The regulated crystallization of perovskite and highly repeatable preparation are decisive challenges for large-scale flexible perovskite solar cells(PSCs).Herein,we synthesize an oil-soluble poly(3,4-ethylenedioxythiophene)(Oil-PEDOT)as a hole transport layer(HTL).The non-wetting Oil-PEDOT HTL can promote the quality of large-area flexible perovskite films because of its optimized crystallinity and printability.The Oil-PEDOT layer also delivers desirable conductivity and charge transport without a complex doping.Consequently,the flexible PSCs with Oil-PEDOT HTL achieve an efficiency of 19.51%and 16.70%based on 1.05 and 22.50 cm^(2),respectively.Moreover,these large-scale flexible PSCs demonstrate remarkable mechanical robustness,and the efficiency exhibits 93%retention after 7,000 bending cycles.These results show that the Oil-PEDOT is a potentially efficient HTL for fabricating efficient large-scale flexible PSCs.

Reducing Energy Loss and Morphology Optimization Manipulated by Molecular Geometry Engineering for Hetero-junction Organic Solar Cells

of main observation and conclusion Molecular geometry engineering is an efective strategy to control the micromorphology and molecularenergy level in organic photovoltaics(OPVs).Two novel copolymers based on alkysilyl-and chloride-functionalied benzodithiophene(BDT)were designed and synthesized for wide bandgap copolymer donor materials in OPVs.It was found that the two copolymers exhited distinctly different proper-ties in active layer when blended with fulerene-fre acceptor T-4.The chloride-functionalited copolymer PBDTCI-TZ2 with deeper molecular energy leveland better coplanar structure induced more ordered aggregation in blend flm.Thus,the device based on PBDTC-TZ exhibits better energy alinmentwith IT-4F and smallr radiative recombination.furthermore,the non-radiative recombination of PBDTCI-TZ.T-4F based device is about 45 mV lowerthan the PBDTS-TZ/T-4F based device,contributing to a lower enery loss(Ein,and a higher open-cicut voltage(Vc).As a resut,the devices based onthe blend of PBDTC-TZ2.IT-4F exhibit a high power conversion efficiency(PCE)of up to 12.2%with a high Vvoe of 0.837 Vv,higher than that of PBDTSi-TZ:IT-4F,of which the PCE is 11.2%with a Voc of 0.781V.

Molecular crowding agents engineered to make bioinspired electrolytes for high-voltage aqueous supercapacitors

The development of low-cost and eco-friendly aqueous electrolytes with a wide voltage window is the key to achieving safe high energy density supercapacitors(SCs).In this work,a molecular crowding electrolyte is prepared by simulating the crowded environment in living cells.Ion transport in the molecular crowding electrolyte can be effectively improved via reducing the molecular weight of the crowding agent,polyethylene glycol(PEG).The results show that PEG with a molecular weight of 200(PEG200)can significantly improve ionic conductivity while maintaining a wide voltage window.These advantages enable commercial activated carbon-based SCs to work at 2.5 V with high energy density,outstanding rate performance and good stability for more than 10,000 cycles.On this basis,three series of molecular crowding electrolytes using sodium perchlorate,lithium perchlorate,and sodium trifluoromethanesulfonate as salts are developed,demonstrating the versatility of PEG200 for wide-voltage aqueous electrolytes.

Large-area Flexible Organic Solar Cells: Printing Technologies and Modular Design

Flexibility is the most prominent advantage of organic solar cells(OSCs) compared with traditional photovoltaic devices, showing an irreplaceable commercial potential. Currently, the maximum power conversion efficiencies(PCEs) of single-junction OSCs have been over 19% and 16% upon rigid and flexible substrates, respectively, which meet the criteria for commercial application. Extensive research efforts are under way, such as device configuration design, interface/photosensitive layer synthesis, transparent electrode modification and printing technology innovation, however, the reasonable selection of printing technologies, the huge performance loss of large-area printing process and the structural design of flexible modules are still the bottlenecks, limiting the commercialization of OSCs. This review focuses on the technical challenges and rational modular configuration design for printing preparation of flexible high-efficiency large-area organic devices, from the aspects of the functional layer material selection, printing process research status and large-scale efficiency losses. These will promote the integrated applications of printable organic semiconductor materials for next-generation clean energy and appeal extensive attentions in wearable electronics, building-integrated photovoltaics and Internet of Things, etc.

Enriching redox active sites by interconnected nanowalls-like nickel cobalt phospho-sulfide nanosheets for high performance supercapacitors

Although transition metal phospho-sulfides deliver outstanding electrochemical performance,complex preparation methods hindered their further development.Herein,we report a facile one-step electrodeposition approach to deposit interconnected nanowalls-like nickel cobalt phospho-sulfide(Ni-Co-P-S)nanosheets onto the surface of carbon cloth.The thin Ni-Co-P-S nanosheets with multi-components and synergetic effects delivered rich active sites,further enhancing reversible capacitance.Therefore,the as-prepared Ni-Co-P-S electrode materials exhibit excellent electrochemical performance in a three-electrode system,showcasing a high specific capacitance of 2744 F/g at 4 A/g.The full supercapacitors based on Ni-Co-P-S as positive electrode and active carbon as negative electrode showcase a high specific capacitance of 110.9 F/g at 1 A/g,impressive energy density of 39.4 Wh/kg at a power density of 797.5 W/kg in terms of excellent cycling stability(91.87%retention after 10,000 cycles).This simple electrode position strategy for synthesizing Ni-Co-P-S can be extended to prepare electrode materials for various sustainable electrochemical energy storage/conversion technologies.

Hierarchically nitrogen-doped mesoporous carbon nanospheres with dual ion adsorption capability for superior rate and ultra-stable zinc ion hybrid supercapacitors

Although significant progress has been achieved in developing high energy aqueous zinc ion hybrid supercapacitors(ZHSCs),the sluggish diffusion of zinc ion(Zn^(2+))and unsatisfactory cathodes still hinder their energy density and cycling life span.This work demonstrates the use of nitrogen-doped mesoporous carbon nanospheres(NMCSs)with appropriately hierarchical pore distribution and enhanced zinc ion storage capability for efficient Zn^(2+)storage.The asprepared aqueous ZHSC delivers a significant specific capacity of 157.8 mA h g^(-1),a maximum energy density of 126.2 W h kg^(-1) at 0.2 A g^(-1),and an ultra-high power density of 39.9 kW kg^(-1) with a quick charge time of 5.5 s.Furthermore,the ZHSC demonstrates an ultra-long cycling life span of 50,000 cycles with an exciting capacity retention of 96.2%.More interestingly,a new type of planar ZHSC is fabricated with outstanding low-temperature electrochemical performance,landmark volumetric energy density of 31.6 mW h cm^(-3),and excellent serial and parallel integration.Mechanism investigation verifies that the superior electrochemical capability is due to the synergistic effect of cation and anion adsorption,as well as the reversible chemical adsorption of NMCSs.This work provides not only an innovative strategy to construct and develop novel high-performance ZHSCs,but also a deeper understanding of the electrochemical characteristics of ZHSCs.

Bending-stability Interfacial Layer as Dual Electron Transport Layer for Flexible Organic Photovoltaics

The flexibility of organic photovoltaics(OPVs)has attracted worldwide attention in recent years.To realize the bending-stability of OPVs,it is necessary to put forward the bending-stability of interfacial layer.A novel bendable composite is explored and successfully applied as an electron transport layer(ETL)for fully-flexible OPVs.We incorporated poly(vinylpyrrolidone)(PVP)into conjugated electrolytes(CPE)to composite a bendable ETL for high-performance OPVs devices.Fortunately,the devices based on PVP-modified CPE exhibited better device performances and more excellent mechanical properties of bendability.The fullerene-free OPVs based on PM6:IT-4 F with CPE@PVP as ETLs yield the best power conversion efficiency(PCE)of 13.42%.Moreover,a satisfying efficiency of 12.59%has been obtained for the fully-flexible OPVs.As far as we know,this is one of the highest PCE for fully-flexible OPV based PM6:IT-4 F system.More importantly,the flexible OPVs devices can retain more than 80%of its initial efficiency after 5000 bending cycles.Furthermore,among various curvature radii,the mechanical properties of the device based on CPE@PVP are superior to those of the device based on bare CPE as ETL.These findings indicate that the functional flexibility of CPE as a cathode interfacial layer is an effective strategy to fabricate high-performance flexible devices in the near future.

Colloidal chemistry in perovskite precursor solution

As an outstanding energy-harvesting technology,perovskite solar cells(PSCs)have gained much attention due to the excellent photoelectric performance.The performance of PSCs has been promoted to achieve breakthroughs repeatedly with composition regulation,interface engineering,additive strategy and so on.To date,the certification efficiency of PSCs has reached 25.5%with a great commercial feasibility(https://www.nrel.gov/pv/cell-efficiency.html).