Banana-shaped electron acceptors with an electron-rich core fragment and 3D packing capability

The emergence of Y6-type nonfullerene acceptors has greatly enhanced the power conversion efficiency(PCE)of organic solar cells(OSCs).However,which structural feature is responsible for the excellent photovoltaic performance is still under debate.In this study,two Y6-like acceptors BDOTP-1 and BDOTP-2 were designed.Different from previous Y6-type acceptors featuring an A–D–Aʹ–D–A structure,BDOTP-1,and BDOTP-2 have no electron-deficient Aʹfragment in the core unit.Instead,there is an electron-rich dibenzodioxine fragment in the core.Although this modification leads to a marked change in the molecular dipole moment,electrostatic potential,frontier orbitals,and energy levels,BDOTP acceptors retain similar three-dimensional packing capability as Y6-type acceptors due to the similar banana-shaped molecular configuration.BDOTP acceptors show good performance in OSCs.High PCEs of up to 18.51%(certified 17.9%)are achieved.This study suggests that the banana-shaped configuration instead of the A–D–Aʹ–D–A structure is likely to be the determining factor in realizing high photovoltaic performance.

Dopant-free small molecule hole transport materials based on triphenylamine derivatives for perovskite solar cells

In the past decade,perovskite solar cells have become a promising candidate in the photovoltaic industry owing to their high power conversion efficiency that surpasses 25%.However,there are certain limitations that have hindered the development and full-scale practical application of these cells,including the high cost and degradation of perovskite caused by the dopants.Hence,there is an urgent need to develop dopant-free hole transport materials(HTMs).In recent years,HTMs based on triphenylamine(TPA-HTMs)are receiving growing interest owing to their high hole mobility,excellent film formation,and suitable energy levels.The literature here covers work relevant to TPA-HTMs in the last five years.They have been classified according to different core types.The correlations between performance and structure are summarized,and the future development trend of TPA-HTMs is highlighted.

Fluorine-Mediated Benzothiadiazole Derivatives for Second-Order Nonlinear Optics

With increasing research interests in the field of light-matter interactions,various methods have been developed for regulating nonlinear optical(NLO)materials.However,the design and synthesis of organic molecular materials for second-order nonlinear optics remain a great challenge because of the strict requirement of the materials to possess a noncentrosymmetric structure.In this work,two benzothiadiazole(BTD)derivatives referred to as BTD-H and BTD-F were synthesized,and their NLO properties in the crystalline states were studied.It was found that introducing fluorine into the BTD backbone effectively tuned the crystal packing styles of BTD derivatives to a noncentrosymmetric system for effective second-order NLO responses.Such a strategy to induce the noncentrosymmetric structure by introducing the fluorine atoms and halogen interactions may provide guidance for future engineering of organic NLO molecular materials.

Preparation of water-soluble magnetic nanoparticles with controllable silica coating

This work provides a general method for preparing monodisperse, water-soluble and paramagnetic magnetic nanoparticles which are easy to be modified. Firstly, magnetic silica with core-shell structure was prepared according to a previous work. Then, the magnetic silica was treated with alkali solution to afford magnetic nanoparticles. With the increase of calcination temperature for the preparation of magnetic silica, the crystallinity and the magnetic responsibility of magnetic silica strengthened, meanwhile, the corresponding magnetic nanoparticles kept monodisperse without any aggregation. The magnetic nanoparticles are comprised of cobalt ferrite and a silica coating. The silica coating on the cobalt ferrite facilitates the magnetic nanoparticles well-dissolved and monodisperse in water, and easilv modified.

A tunable ionic covalent organic framework platform for efficient CO_(2) catalytic conversion

The cycloaddition reaction between epoxides and CO_(2) is an effective method to utilize CO_(2) resource.Covalent organic frameworks(COFs)provide a promising platform for the catalytic CO_(2) transformations on account of their remarkable chemical and physical properties.Herein,a family of novel vinylene-linked ionic COFs named TE-COFs(TTE-COF,TME-COF,TPE-COF,TBE-COF)has been facilely synthesized from N-ethyl2,4,6-trimethylpyridinium bromide and a series of triphenyl aromatic aldehydes involving different numbers of nitrogen atoms in the central aromatic ring.The resulting catalyst TTE-COF with excellent adsorption capacity(45.6 cm3·g^(-1),273 K)exhibited outstanding catalytic performance,remarkable recyclability and great substrate tolerance.Moreover,it was also observed that the introduction of nitrogen atom in the precursor led to a great improvement in the crystallinity and CO_(2) adsorption capacity of TE-COFs,thus resulting to a progressively improved catalytic performance.This work not only illustrated the influence of monomer nitrogen content on the crystallinity and CO_(2) adsorption capacity of TE-COFs but also provided a green heterogeneous candidate for catalyzing the cycloaddition between CO_(2) and epoxides,which shed a light on improving the catalytic performance of the CO_(2) cycloaddition reaction by designing the covalent organic frameworks structures.

In-situ doping strategy for improving the photocatalytic hydrogen evolution performance of covalent triazine frameworks

A highly conjugated network of covalent triazine frameworks(CTFs)on the one hand promotes light-harvesting,but on the other hand,also results in high carrier recombination which eventually limits their photocatalytic hydrogen evolution reaction(HER)rates.Thus,strategies to favorably tune the electronic configuration of CTFs for efficient photocatalytic HERs need to be developed,but still remain challenging.Herein,a simple in-situ defect strategy involving element doping is developed for the first time to introduce a heteroatom including S and Se into CTF-1 via the condensation of aldehydes with the mixture of the terephthalimidamide and the S-or Se-substituted terephthalimidamide under mild conditions.The doping content(X)is varied,resulting in a series of S-and Se-doped CTFs,named CTFS-1-X and CTFSe-1-X,respectively.Interestingly,for the S-doped CTFs,CTFS-1-10 shows the most excellent HER rate(4,992.3μmol g^(-1)h^(-1))from water splitting,while for the Se-doped ones,CTFSe-1-10 exhibits a photocatalytic HER rate of 5,792.8μmol g^(-1)h^(-1),both of which far surpass undoped CTFs(693.3μmol g^(-1)h^(-1)).In-depth studies indicate that the introduction of S or Se atoms into CTFs could extend the light absorption and promote photo-generated electron-hole pairs migration.Meanwhile,S-or Se-doping could create heterogeneous electronic configuration in CTFs,which can help to suppress carrier recombination.

MOF-COF框架杂化材料

金属有机框架(MOF)和共价有机框架(COF)材料是两种多孔的晶态材料,具备较大的比表面积、高的孔隙率,结构合成修饰方法丰富,因此在析氢、析氧、CO_(2)还原、有机物降解、气体分离等多个方面都有应用前景。但MOF、COF自身仍有许多缺点,如MOF在水溶液中不稳定,结构易塌陷,COF无金属节点,功能较简单,催化性能有待进一步提高等。近年来,MOF-COF核壳杂化材料结合两种材料的优势解决各自的一些缺陷,有广泛的应用潜力,作为新的发展方向受到了关注。本文从MOF-COF杂化材料的类型、合成方法、应用等三个方面综述了近些年来MOF-COF材料的发展状况,并做出了展望。

Thiolactone copolymer donor gifts organic solar cells a 16.72% efficiency

Since 1995,bulk-heterojunction organic solar cells consisting of one or two organic donors and one or two organic acceptors have been fighting for high power conversion efficiencies(PCEs)and good stability[1].Until recent years,this next-generation photovoltaic technology starts to offer decent PCEs,shedding the light on commercialization,and attracting great attention again[2-14].Compared w让h the continuously emerging highperformance nonfullerene acceptors,high-performance donors are rare.

Fused-ring bislactone building blocks for polymer donors

The past 5 years have witnessed the rapid development of organic solar cells based on nonfullerene acceptors(NFAs)[1-26].The state-of-the-art NFA-based single-junction and tandem solar cells afforded 18.22%(certified 17.6%)and 17.36%(certified 17.29%)power conversion efficiencies(PCEs),respectively[27,28].Wide-bandgap(WBG)polymer donors are ideal partners for NFAs.They present complementary absorption with that of low-bandgap NFAs and deep the highest occupied molecular orbital(HOMO)levels.Therefore,solar cells based on a WBG polymer and a NFA can generate high short-circuit current density(Jsc)and open-circuit voltage(Voc)[29].Meanwhile,some WBG polymers show high crystallinity and mobility,gifting the solar cells high fill factors(FF)[30].Recently,our group first reported efficient WBG D-A copolymer donors based on fused-ring aromatic lactone(FRAL)acceptor units.

Preparation of dye-sensitized solar cells with high photocurrent and photovoltage by using mesoporous titanium dioxide particles as photoanode material

Several mesoporous TiO2 （MT） materials were synthesized under different conditions following a hydrothermal procedure using poly（ethylene-glycol）- block-poly（propylene-glycol）-block-poly（ethylene-glycol） （P123） as the template and titanium isopropoxide as the titanium source. The molar ratios of Ti/P123, and the pH values of the reaction solution in an autoclave were investigated. Various techniques such as Brunauer-Emmett-Teller （BET）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, laser Raman spectrometry （LRS）, scanning electron microscopy （SEM）, and high-resolution transmission electron microscopy （HRTEM） were used to characterize the products. Then, these materials were assembled into dye-sensitized solar cells （DSSCs）. Analysis of the J-V curves and electrochemical impedance spectroscopy （EIS） were applied to characterize the cells. The results indicated that the specific surface area and crystalline structure of these materials provide the possibility of high photocurrent for the cells, and that the structural characteristics of the specimens led to increased electron transfer resistance of the cells, which was beneficial for the improvement of the photovoltage of the DSSCs. The highest photoelectric conversion efficiency of the cells involving MT materials reached 8.33%, which, compared with that of P25- based solar cell （5.88%）, increased by 41.7%.

Blue emitting CsPbBr3 perovskite quantum dot inks obtained from sustained release tablets

Blue emitting perovskite ink obtained from cesium lead halide quantum dots bearing chlorine(CsPbClxBr3-x,0<x<3)suffers from the low photoluminescence quantum yield and poor stability.Cesium lead bromine(CsPbBr3)quantum dots free of chlori ne have more stable crystalstructure and fewer crystal defects.Precise control of crystal sizes and surface passivation comporients of CsPbBr3 quantum dots is crucial for the best use of quantum confinement effect and blueshift of emission wavelength to blue region.Here,by polymerizing acrylamide under UV-light irradiation to form polymer gel networks in dimethyl sulfoxide(DMSO)with CsPbBr3 precursors and passivating agents trapped,wesuccessfully prepared novel sustained release tablets with different shapes and sizes.Thanks to the limitation of the polymer networks onsolve nt releasi ng,the resulting CsPbBr3 qua ntum dots have the average size of 1.1±0.2 nm.On the basis of the excelle nt quantum confin eme nteffect and optimized surface passivation,the obtained PQD ink can emit high quality blue light for more than 6 weeks.This work elucidates anew and convenient technique to prepare blue emission perovskite quantum dots ink with high stability and photoluminescence qua ntumyield and provides a great potential technology for the preparation of perovskite optoelectronic devices.

Multi-functional 3D N-doped TiO2 microspheres used as scattering layers for dye-sensitized solar cells

Three-dimensional TiO2 microspheres doped with N were synthesized by a simple single-step solvothermal method and the sample treated for 15 h （hereafter called TMF） was then used as scattering layers in the photoanodes of dye-sensitized solar cells （DSSCs）. The TMF was characterized using scanning electron micro- scopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller measurements, X-ray diffraction, and X-ray photoelectron spectroscopy. The TMF had a high surface area of 93.2 m2. g-~ which was beneficial for more dye-loading. Five photoanode films with different internal structures were fabricated by printing different numbers of TMF scattering layers on fluorine-doped tin oxide glass. UV-vis diffuse reflection spectra, incident photon-to-current efficiencies, photocurrent-voltage curves and electrochemical impedance spectroscopy were used to investigate the optical and electrochemical proper- ties of these photoanodes in DSSCs. The presence of nitrogen in the TMF changed the TMF microstructure, which led to a higher open circuit voltage and a longer electron lifetime. In addition, the presence of the nitrogen significantly improved the light utilization and photocur- rent. The highest photoelectric conversion efficiency achieved was 8.08%, which is much higher than that derived from typical P25 nanoparticles （6.52%）.

Metallocorrole-based porous organic polymers as a heterogeneous catalytic nanoplatform for efficient carbon dioxide conversion

Metallocorrole macrocycles that represent a burgeoning class of attractive metal-complexes from the porphyrinoid family,have attracted great interest in recent years owing to their unique structure and excellent performance revealed in many fields,yet further functionalization through incorporating these motifs into porous nanomaterials employing the bottom-up approach is still scarce and remains synthetically challenging.Here,we report the targeted synthesis of porous organic polymers(POPs)constructed from custom-designed Mn and Fe-corrole complex building units,respectively denoted as CorPOP-1(Mn)and CorPOP-1(FeCl).Specifically,the robust CorPOP-1(Mn)bearing Mn-corrole active centers displays superior heterogeneous catalytic activity toward solvent-free cycloaddition of carbon dioxide(CO_(2))with epoxides to form cyclic carbonates under mild reaction conditions as compared with the homogeneous counterpart.CorPOP-1(Mn)can be easily recycled and does not show significant loss of reactivity after seven successive cycles.This work highlights the potential of metallocorrole-based porous solid catalysts for targeting CO_(2) transformations,and would provide a guide for the task-specific development of more corrole-based multifunctional materials for extended applications.

Solvent induced enhancement of nonlinear optical response of graphdiyne

Flat and crystalline materials with exceptional nonlinear optical(NLO) properties are highly desirable for their potential applications in integrated NLO photonic devices.Graphdiyne(GD),a new twodimensional(2 D) carbon allotrope,has recently evoked burgeoning research attention by virtue of its tunable bandgap along with a high carrier mobility and extended π-conjugation compared with most conventional optical materials.Here,we experimentally probe the third-order nonlinear optical response of GD dispersed in several common solvents(alcohols) using a femtosecond Z-scan technique.The measured nonlinear optical refractive index is in the order of ~10^(-8) cm^(2)/W,which is approximately one order of magnitude higher than that of most 2 D materials.In particular,we find that different NLO responses can be observed from GD when dispersed in different solvents,with the strongest NLO response when dispersed in 1-propanol.It is proposed that some intrinsic properties of the solvents,such as the polarity and viscosity,could influence the NLO response of GD materials.Our experimental results confirm the assumptions on the NLO behavior in GD and demonstrate its great potential for future generations of Kerr-effect-based NLO materials and devices.

Oxygen vacancies effects on phase diagram of epitaxial La1-xSrxMnO3 thin films

We investigated the effects of oxygen vacancies on the structural, magnetic, and transport properties of Lal-xSrxMnO3 （x=0.1, 0.2, 0.33, 0.4, and 0.5） grown around a critical point （without/with oxygen vacancies） under low oxygen pressure （10 Pa） and high oxygen pressure （40 Pa）. We found that all films exhibit ferromagnetic behavior below the magnetic critical temperature, and that the films grown under low oxygen pressures have degraded magnetic properties with lower Curie temperatures and smaller magnetic moments. These results show that in epitaxial La1-xSrxMnO3 thin films, the magnetic and transport properties are very sensitive to doping concentration and oxygen vacancies. Phase diagrams of the films based on the doping concentration and oxygen vacancies were plotted and discussed.