Ionic Liquid Assisted Imprint for Efficient and Stable Quasi-2D Perovskite Solar Cells with Controlled Phase Distribution

Although two-dimensional perovskite devices are highly stable,they also lead to a number of challenges.For instance,the introduction of large organic amines makes crystallization process complicated,causing problems such as generally small grain size and blocked charge transfer.In this work,imprint assisted with methylamine acetate were used to improve the morphology of the film,optimize the internal phase distribution,and enhance the charge transfer of the perovskite film.Specifically,imprint promoted the dispersion of spacer cations in the recrystallization process with the assistance of methylamine acetate,thus inhibited the formation of low-n phase induced by the aggregation of spacer cations and facilitated the formation of 3D-like phase.In this case,the corresponding quasi-2D perovskite solar cells delivered improved efficiency and exhibited superior stability.Our work provides an effective strategy to obtain uniform phase distribution for quasi-2D perovskite.

The Crystallization Behavior of L-Poly(lactic acid)/Polypropylene Blends:The Acceleration for Both L-Poly(lactic acid)and Polypropylene

For a polymer/polymer dismissible blend with two crystallizable components,the crystallization behavior of different components and the reciprocal influences between different crystals are interesting and important,but did not investigate in detail.In this study,the L-poly(lactic acid)/polypropylene(PLLA/PP)blends with different weight ratios were prepared by melt mixing and the crystallization behavior of the blends were investigated.Results showed that the crystalline structures of PLLA and PP were not altered by the composition.For the crystallization of PLLA,both the diffusion of chain segments and crystallization rate were enhanced under the existence of PP crystals.For the crystallization of PP,its crystallization rate was depressed under the existence of amorphous PLLA molecular chains.When the PP crystallized from the existence of PLLA crystals,although the diffusion rate of PP was reduced by PLLA crystals,the nucleation positions were obviously enhanced,which accelerated the formation of PP crystals.This investigation would supply more basic data for the application of PLLA/PP blend.

Random Terpolymer Based on Simple Siloxane-functionalized Thiophene Unit Enabling High-performance Non-fullerene Organic Solar Cells

Incorporation of siloxane-functionalized units into polymers backbone has proven to be an efficient strategy to improve photovoltaic performance. In this work, a low-cost siloxane-containing unit was developed to construct a series of terpolymers, and the effects of siloxane on the polymer performance were systematically studied. Different contents of thiophene containing siloxane-functionalized side chain were introduced into PM6 to obtain a series of polymers(PM6, PM6-SiO-10, PM6-SiO-20 and PM6-SiO-30). The siloxane-functionalized side chains in polymers have only a slight effect on the absorption behavior and frontier molecular orbitals. However, when the siloxane content increased, the terpolymers' aggregation property decreased and the temperature-dependency increased, leading to improved donor-acceptor compatibility. The power conversion efficiency(PCE) based on PM6:Y6, PM6-SiO-20:Y6 and PM6-SiO-30:Y6 devices was 15.64%, 16.03% and 15.82%, respectively. In comparison, the active layer based on PM6-SiO-10:Y6 exhibits the most appropriate phase separation morphology, resulting in effective exciton dissociation, more balanced hole-electron transport and less recombination. Consequently, the highest PCE of 16.69% with an outstanding shortcircuit current density of 26.96 mA·cm^(-2) was obtained, which are one of the highest values for siloxane-functionalized polymer-based devices.This work demonstrates that finely controlling the content of siloxane-functionalized thiophene is beneficial for obtaining high-performance terpolymer donors and provides a novel and low-cost method to improve photovoltaic performance.

Achieving improved stability and minimal non-radiative recombination loss for over 18%binary organic photovoltaics via versatile interfacial regulation strategy

Interfacial regulation,serving multiple roles,is critical for the fabrication of stable and efficient organic photovoltaics(OPVs).Herein,a multifunctional cathode interlayer PDINO(15 nm)is prepared by regulating film thickness,which is inserted between active components and stable silver electrode to align work function,and maintain good interfacial contact and device stability.The thick film can help to reduce interfacial surface defects,keep stable surface morphology,and block the silver diffusion into the active layer.Consequently,the optimal PM6:Y6 device records an impressive power conversion efficiency(PCE)of 17.48%with minimized non-radiative recombination loss of 0.239 V.More importantly,the unencapsulated device maintains 91%of the original PCE after aging for over 60 days at 25℃ and 10%relative humidity in dark conditions.Meanwhile,the PM6:eC9 device achieves a remarkable PCE of 18.22%with the enhancement of open-circuit voltage(V_(oc)).Furthermore,the 1 cm^(2) device-based PDINO(15 nm)/Ag shows a high PCE of 15.2%while only 12.6%for PDINO(9 nm)/Al,indicating the good compatibility of PDINO(15 nm)interlayer with the R2R coating processes used in large-area OPVs fabrication.This work highlights the promise of interfacial regulation to simultaneously stabilize and enhance the efficiency of organic photovoltaics.

Improving Ultraviolet Stability of Perovskite Solar Cells via Singlet Fission Down-Conversion

The instability of perovskite materials under continuous ultraviolet(UV)light irradiation and high sensitivity in humid environments remain obstacles to future commercialization.Especially,the photovoltaic performance of perovskite solar cells(PVSCs)is prone to decline under UV light exposure for sustained periods of time.However,in conventional methods,preventing UV light from entering PVSCs usually comes at the expense of reducing short circuit photocurrent(Jsc).Herein,the UV stability of PVSCs is modified by in-troducing a singlet fission down-conversion layer 6,13-bis(triisopropylsilylethynyl)pentacene(TIPS-PEN)via one-step anti-solvent method without sacrificing device efficiency.The introduction of down conversion layer can not only improve the Jsc by converting UV light into multiple excitons,but also enhance the open-circuit voltage(Voc)owing to a better matched energy level alignment at the perovskite/spiro-OMeTAD interface.Consequently,the TIPS-PEN incorporated PVSCs attain the champion power conversion effi-ciency(PCE)up to 22.92%accompanied with dramatically increased UV photostability which can retain 80%of its primitive PCE un-der continuous UV light soaking for 150 h.Moreover,the unencapsulated PVSCs with TIPS-PEN exhibit remarkable moisture stability which can sustain over 80%of the initial value under air conditions(50%relative humidity,25℃)after 1000 h.

Contact Electrification Spectrum for Performance Enhancement Mechanism Investigation of Triboelectric Nanogenerators based on Silicone Elastomers with Different Surface Microstructures

Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables,Internet of Things(IoTs),etc.The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs,but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design.Taking advantages of the surface-sensitive characteristic of CE effect,this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs.Firstly,four different kinds of surface microstructures,namely planar surface(PS)and three combinations of two basic surface microstructures,i.e.,micro lens arrays(MLAs),fabric textures(FTs),and hierarchical structures of MLAs on FTs(MLA/FTs),were elaborately designed and introduced for an identical triboelectric material(i.e.,silicone elastomer)by a(micro)molding synthesis route.Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions.Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine,it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density,effective contact area and contacting/separating velocity,rather than simple increase of its surface area.

Carbazolebis(thiadiazole)-core based non-fused ring electron acceptors for efficient organic solar cells

Non-fused ring electron acceptors(NFREAs)have a broad application prospect in the commercialization of organic solar cells(OSCs)due to the advantages of simple synthesis and low cost.The selection of intermediate block cores of non-fused frameworks and the establishment of the relationship between molecular structure and device performance are crucial for the realization of high-performance OSCs.Herein,two A-D-A’-D-A type NFREAs namely CBTBO-4F and CBTBO-4Cl,constructed with a novel electron-deficient block unit N-(2-butyloctyl)-carbazole[3,4-c:5,6-c]bis[1,2,5]thiadiazole(CBT)and bridging unit 4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene(DTC)coupling with different terminals(IC-2F/2Cl),were designed and synthesized.The two NFREAs feature broad and strong photoresponse from 500 nm to 900 nm due to the strong intramolecular charge transfer characteristics.Compared with CBTBO-4F,CBTBO-4Cl shows better molecular planarity,stronger crystallinity,more ordered molecular stacking,larger van der Waals surface,lower energy level and better active layer morphology,contributing to much better charge separation and transport behaviors in its based devices.As a result,the CBTBO-4Cl based device obtains a higher power conversion efficiency of 10.18%with an open-circuit voltage of 0.80 V and a short-circuit current density of 21.20 mA/cm^(2).These results not only demonstrate the great potential of CBT,a new building block of the benzothiazole family,in the construction of high-performance organic conjugated semiconductors,but also suggest that the terminal chlorination is an effective strategy to improve device performance.

通过晶格加固实现多环境下相稳定的高效钙钛矿太阳电池

富甲脒体系的钙钛矿太阳电池(PSCs)由于出色的热稳定性和较宽的光谱吸收范围,在商业应用中显示出竞争力.然而,富甲脒体系的PSCs会受到残余应力的极大影响,出现晶格过度扭曲并诱发不利的相变.本文通过构建一系列的晶格加固结构,验证了有机间隔阳离子和无机八面体之间的差异性相互作用.通过探索α相到γ相以及δ相的转变过程,揭示了残余应力释放和晶格加固之间的关系及其重要性.最后,苯甲基胺修饰的器件展现出最高22.90%的光电转换效率(PCE),并抑制了多路径相变.在空气中放置1000小时后,初始性能仍能维持初始值的90%.此外,在25平方厘米的衬底上制备了PCE为17.10%的迷你模组,验证了大面积制备的可行性.

Enhancing photostability and power conversion efficiency of organic solar cells by a “sunscreen” ternary strategy

The field has witnessed the rapid growth in the power conversion efficiency(PCE)of organic solar cells(OSCs)over the past decade,reaching the threshold for practical commercialization.However,a major issue remains that OSC lifetimes are seriously limited by the ultraviolet(UV)-induced photodegradation.Here,inspired by the superior photostability of car paint under sunlight and ambient air,a“sunscreen”molecule,2-(2-hydroxy-5-tert-octylphenyl)benzotriazole(UV329),is used to construct the PM6:Y6 ternary device.The addition of UV329 mainly enhances the ordered stacking of PM6 and increases the light utilization of blend films with the improved crystallization and appropriate phase separation.Accordingly,the ternary device exhibits stronger light response and obviously higher and more balanced carrier mobilities,contributing to higher short-circuit current density,fill factor and PCE.Similar PCE boost is also verified in PM6:BTP-e C9 and PM6:L8-BO systems.The photodegradation of PM6 dominates the photo-degradation process of PM6:Y6 systems,while the UV329 can effectively suppress such degradation,and thus the ternary device can retain nearly 90%of the initial PCE under continuous illumination for 120 min.Moreover,ternary devices also preserve better thermal stability and shelf-life with the enhanced PCE.This work provides a simple yet effective strategy for simultaneously improving PCE and photostability of OSCs.

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids)for Efficient and Stable Perovskite Solar Cells

The inevitable ion migration that occurs within ionic polycrystalline perovskite film results in inferior longterm stability of perovskite solar cells(PVSCs)that cannot meet the commercial requirements.Here,a novel poly(ionic liquid)named poly-1-vinyl-3-propyltrimethoxysilane imidazolium chloride(PImIL-SiO)is first introduced into perovskite to strengthen grain boundaries(GBs)and construct dual-functional barriers against internal ion migration and external moisture erosion for fabricating highly efficient and stable PVSCs.PImIL-SiO-containing imidazoliumcations and pendant siloxane groups contribute to passivation of bulk defects and anchoring of GBs,which effectively hinders ion migration channels,thus reducing perovskite film phase separation and device hysteresis.Furthermore,the intrinsically hydrophobic PImIL-SiO automatically forms a secondary protective barrier to endow the perovskite film with ultrahigh moisture corrosion resistance through the hydrolyzation reaction of siloxane with the permeated moisture.Consequently,the PImIL-SiO-modified PVSCs achieve a champion power conversion efficiency(PCE)of 22.46%,accompaniedby excellent thermal andhumidity stabilities where the non-encapsulated devices retain 87%of the initial PCE after aging at 85℃for 250 h and>85%of the initial PCE over 1100 h in air with a relative humidity of 50–70%.

Recent Progresses on Dopant-Free Organic Hole Transport Materials toward Efficient and Stable Perovskite Solar Cells

As the third generation new battery,the power conversion efficiency(PCE)of metal halide perovskite solar cells(PsCs)has increased from 3.8%in 2009 to 25.8%currently certified,which fully shows that they have great research value and development prospect.As one of the main components of high-efficiency PSCs,hole transport materials(HTMs)play an important role in extracting and transporting holes and inhibiting charge recombination.However,commonly used HTMs require doping,and the hygroscopicity and corrosiveness of the dopants will destroy the stability of PsCs and hinder their commercialization.Therefore,it is of great significance to develop dopant-free HTMs.

A Facile Strategy to Enhance the Formation of Stereocomplex Crystallites in Poly(L-lactic acid)/Poly(D-lactic acid) Blend with High Molecular Weights

Blending of poly(levorotatory-lactic acid) (PLLA) and poly(dextrorotatory-lactic acid) (PDLA) produces the stereocomplex crystallites (PLA SC), which present higher melting temperature and mechanical properties than that of neat PLLA or PDLA. However, in the PLLA/PDLA blends with higher molecular weights, the phase separation occurs and the SC exhibits weak memory after melting, which lead to a small amount of SC together with a large amount of homochiral crystallites (HC) develop during crystallization from the melt. In this study, a small content of graphite oxide was blended with PLLA and PDLA to form ternary blends, and it was exciting to find that the formation of SC was enhanced gradually with the content of graphite oxide. The SC exclusively developed when 2 wt% graphite oxide was incorporated into the PLLA/PDLA, and the crystallinity with ∼50% was received even during fast cooling from the melt (−50 ℃/min). The acceleration formation of SC was speculated due to the interaction between PLA molecular chains and the hydroxyl groups on the surface of graphite oxide and the obstruction of proliferation of graphite oxide.

Highly efficient perovskite solar cells by building 2D/3D perovskite heterojuction in situ for interfacial passivation and energy level adjustment

Passivating the interfacial defects and reducing the interfacial non-radiative recombination losses are the keys to improving the photovoltaic performance of three-dimensional(3D)perovskite solar cells(PVSCs).Stacking two dimensional(2D)perovskites on 3D perovskite is a promising method for interfacial treatment that improves the stability and efficiency of PVSCs.Herein,we developed conjugated fluorinated benzimidazolium cation(FBIm+)which can be inserted between 3D perovskite and holetransporting layer(HTL)to form 2D perovskite in situ.The 2D single crystal structures of(FBIm)_(2)Pb I4and(FBIm)_(2)Pb Br_(4)were achieved and confirmed by single-crystal X-ray diffraction(XRD),while few single crystals of 2D perovskite based on imidazolium or benzimidazolium anchors have been reported.The 2D perovskite can passivate the interfacial defects,induce better crystallinity and orientation,conduct lower trap density and extend carrier lifetime.Furthermore,the energy level arrangement can be regulated by changing the counterion from iodide to bromide,which can efficiently improve the hole extraction and device performances.As a consequence,the best efficiency of 23.00%for FBIm Br-incorporated devices was achieved,while only 20.72%for the control device.Meanwhile,the PVSCs modified by FBIm Br displayed excellent environmental stability due to the constructed hydrophobic 2D perovskite layer which can effectively block moisture permeation.This work develops a new path to design novel conjugated organic passivants to form 2D/3D perovskite structures.

Arranging Electronic Localization of PtCu Nanoalloys to Stimulate Improved Oxygen Electroreduction for High-Performance Fuel Cells

Developing exceptionally durable and efficient oxygen reduction reaction(ORR)catalysts is of paramount importance to the widespread commercialization of proton exchange membrane fuel cells(PEMFCs)but is still challenging.Herein,PtCu nanoalloys rooted on nitrogen-doped carbon nanosheets(PtCuNC-700)with fully exposed PtCu nanoalloys and strong metal–support interaction were developed.Benefiting from its structural and compositional merits,PtCuNC-700 showcases superior ORR activity and stability with a specific activity of 1.05mA cm^(−2)and mass activity of 0.45 A mgPt^(−1),4.2-fold and 3.7-fold higher than Pt/C(0.25 mA cm^(−2)and 0.12 A mgPt^(−1)),respectively.Moreover,PtCuNC-700 exhibits first-class performance in H2/air PEMFC assessment and delivers a peak power density of 929.7 mW cm^(−2)and excellent cycling stability up to 30,000 cycles.Theoretical calculations disclose that the synergistic effect of alloying Pt with Cu combined with the strong interaction between PtCu nanoalloys and nitrogen-doped carbon nanosheets can effectively modify the local electron configuration and density of states of Pt sites approaching the Fermi level.Hence,the PtCu-alloy catalysts realized here diminish the energy barrier for ORR and accelerate their reaction kinetics.This work provides a reliable and effective approach to boost the activity and stability of Pt alloy-based ORR electrocatalysts in PEMFCs.

Breaking the Scaling Relationship Limit:From Single-Atom to Dual-Atom Catalysts

Recent decades have witnessed the rapid development of catalytic science,especially after Taylor and Armstrong proposed the notion of the“active site”in 1925.By optimizing reaction paths and reducing the activation energies of reactions,catalysts appear in more than 90%of chemical production reactions,involving homogeneous catalysis,heterogeneous catalysis,and enzyme catalysis.Because of the 100%efficiency of active atom utilization and the adjustable microenvironment of metal centers,single-atom catalysts(SACs)shine in various catalytic fields for enhancing the rate,conversion,and selectivity of chemical reactions.Nevertheless,a solo active site determines a fixed adsorption mode,and the adsorption energies of intermediates from multistep reactions linking with a solo metal site are related to each other.For a specific multistep reaction,it is almost impossible to optimally adjust the adsorption of every intermediate on the solo site simultaneously.This phenomenon is termed the scaling relationship limit(SRL)and is an unavoidable obstacle in the development of pure SACs.Dual-atom catalysts(DACs),perfectly inheriting the advantages of SACs,can exhibit better catalytic performance than simple SACs and thus have gradually gained researchers’attention.Depending on the dual-metal structure,dual-metal sites(DMSs)in DACs can be divided into two separated heterometal sites,two linked homometal sites,and two linked heterometal sites.Two separated heterometal sites prescribe a distance limit between two metal sites for electron interaction.Currently,the active origins of DACs can be summarized in the following three points:(1)electronic effect,in which only one metal center serves as active site and the other plays an electronic regulatory role;(2)synergistic effect,in which two metal centers separately catalyze different core steps to improve catalytic performance together;(3)adsorption effect,in which offering additional sites changes the adsorption structures to break the SRL based on SACs.Among the three active origins,optimizing the adsorption structure of intermediates upon DMSs is one of the most effective technologies to boost the catalytic property of DACs on the basis of SACs.To date,few contributions have focused on the development of DACs in various heterogeneous catalysis environments,including O_(2) reduction reaction,O_(2) evolution reaction,H_(2) evolution reaction,CO_(2) reduction reaction,N_(2) reduction reaction,and other conversion reactions.In this Account,a summary of recent progress regarding DACs in heterogeneous catalysis will be presented.First,the evolution of DACs from an unpopular discovery to research hot spot is illustrated through a timeline.In the next section,the DACs are divided into three categories,and the potential active origins of DACs are revealed by comparison with SACs.In addition,the techniques for constructing DACs are systematically summarized,including preparation of carbonous,pyrolysis-free,noncarbon-supported,and complex-type DACs.Furthermore,the underlying active origins of DACs in specific energy-and environment-related reactions are introduced in detail with assistance of theoretical calculations.Finally,we affirm the contribution of DACs to catalysis,particularly heterogeneous electrocatalysis,and provide an outlook regarding the development direction for DACs by discussing the major challenges.It is anticipated that this Account can inspire researchers to propel the advance of DACs.