H-and J-aggregation of conjugated small molecules in organic solar cells

As H-and J-aggregation receive more and more attention in the research of organic solar cells(OSCs),especially in small molecular systems,deep understanding of aggregation behavior is needed to guide the design of conjugated small molecular structure and the fabrication process of OSC device.For this end,this review is written.Here,the review firstly introduced the basic information about H-and J-aggregation of conjugated small molecules in OSCs.Then,the characteristics of H-and J-aggregation and the methods to identify them were summarized.Next,it reviewed the research progress of H-and J-aggregation of conjugated small molecules in OSCs,including the factors influencing H-and J-aggregation in thin film and the effects of H-and J-aggregation on OPV performance.

Synergistic Optimization of Buried Interface by Multifunctional Organic-Inorganic Complexes for Highly Efficient Planar Perovskite Solar Cells

For the further improvement of the power conversion efficiency(PCE)and stability of perovskite solar cells(PSCs),the buried interface between the perovskite and the electron transport layer is crucial.However,it is challenging to effectively optimize this interface as it is buried beneath the perovskite film.Herein,we have designed and synthesized a series of multifunctional organic-inorganic(OI)complexes as buried interfacial material to promote electron extraction,as well as the crystal growth of the perovskite.The OI complex with BF4−group not only eliminates oxygen vacancies on the SnO_(2) surface but also balances energy level alignment between SnO_(2) and perovskite,providing a favorable environment for charge carrier extraction.Moreover,OI complex with amine(−NH_(2))functional group can regulate the crystallization of the perovskite film via interaction with PbI2,resulting in highly crystallized perovskite film with large grains and low defect density.Consequently,with rational molecular design,the PSCs with optimal OI complex buried interface layer which contains both BF4−and−NH_(2) functional groups yield a champion device efficiency of 23.69%.More importantly,the resulting unencapsulated device performs excellent ambient stability,maintaining over 90%of its initial efficiency after 2000 h storage,and excellent light stability of 91.5%remaining PCE in the maximum power point tracking measurement(under continuous 100 mW cm−2 light illumination in N2 atmosphere)after 500 h.

Superior aggregation, morphology and photovoltaic performance enabled by fine tuning of fused electron-deficient units in polymer donors

Copolymerization of an electron-rich donor(D)unit with an electron-deficient acceptor(A)unit to construct efficient D-π-A-πtype donors is an effective strategy for organic solar cell applications.The electron-deficient unit fusion,endows extendedπ-conjugation plane and insures excellent photoelectronic property,has great advantages to build A moiety and gradually receives considerable attention.In this work,we adopt benzo[2,1-b:3,4-b’]dithiophene and benzopyrazine(BP),benzothiadiazole(BT)and benzoselenadiazole(BS)to cleverly construct a series of fused A units with different electrondeficient ability,and further synthesize three polymer donors PBDP-BP,PBDP-BT,and PBDP-BS,respectively.The relationships between structure and performance were systematically investigated.PBDPBT shows a moderate aggregation behavior in both solution and film,and the highest hole mobility among the three polymers.After blending with Y6,the PBDP-BT:Y6-based film has the strongest absorption,favorable compatibility,superior crystallinity,and uniform phase separation morphology compared with PBDP-BP or PBDP-BS based blend films.Thus,the device based on PBDP-BT:Y6 has the highest and balanced charge mobility,suppressive recombination,reduced energy loss and achieves an outstanding PCE of 15.14%,which is superior to PBDP-BP:Y6(8.55%)and PBDP-BS:Y6(6.85%).These results provide learnable guidelines for future fused electron-deficient unit-based donor design for photovoltaic application.

Chlorinated polymer solar cells simultaneously enhanced by fullerene and non-fullerene ternary strategies

To achieve efficient polymer solar cells(PSCs)with full utilization of the whole spectrum,the multicomponent devices are of great importance to be deeply explored,especially for their capability of one-step fabrication.However,the research about one same binary system simultaneously derivated various multi-component PSC is still very limited.Herein,we achieved the whole constructions from one binary host to different ternary systems and even the quaternary one.The ternary strategies with fullerene acceptor,PC_(71)BM,and non-fullerene acceptor,BT_(6)IC-BO-4Cl,as the third component,both boosted the device efficiencies of PBT4Cl-Bz:IT-4F binary system from about 9% to comparatively beyond 11%.Despite the comparable improvement of performance,there existed other similarities and differences in two ternary strategies.In detail,the isotropic carrier transport of PC_(71)BM which largely elevated the fill factor(FF)in the corresponding devices,while the strong absorption of BT_(6)IC-BO-4Cl enhanced the short current density(J_(SC))most.More interestingly,quaternary devices based on PBT4Cl-Bz:IT-4F:PC71 BM:BT_(6)IC-BO-4Cl could combine both advantages of fullerene and non-fullerene ternary strategies,further pumped the J_(SC) from 16.44 to the highest level of 19.66 mA cm^(-2) among all devices,eventually resulted in an optimized efficiency of 11.69%.It reveals that both fullerene and non-fullerene ternary strategies have their unique feature to elevate the device performance either by efficient isotropic carrier transport or better coverage of whole sunlight spectrum and easy tunable energy levels from organic materials.The key is how to integrate the two pathways in one system and provide a more competitive solution facing high-quality PSCs.

Ternary strategy: An analogue as third component reduces the energy loss and improves the efficiency of polymer solar cells

Ternary strategy is a convenient and effective method to boost the performance of polymer solar cells(PSCs).Utilizing a ternary strategy to trade-off between the energy loss and the efficiency of devices however requires further exploration.Here,through the hydroxyl(-OH)and acetoxy(-OCOMe)substitution atβ-position of the IC terminal group,we developed two new synthetic acceptors,BTIC-OH-βand BTICOCOMe-β,which were designed to confine the morphology aggregation.Introduction of an analogue as the third component provides a simple but efficient way to further balance the short current density(Jsc)and open-circuit voltage(Voc),leading to a champion efficiency based on PBDB-T:PBDB-TF:BTIC-OCOMe-β,effectively as high as 12.45%.The results were examined mainly in terms of the morphology characterization,electroluminescence external quantum efficiency(EQEEL),steady-state photoluminescence(PL)and transient technology.It suggested fine-tuning of the morphology by ratio modulation,reduction of the energy loss,construction of a promising pathway for charge transfer in the ternary system and enhancing the carrier extraction.In this way,a ternary strategy with an analogue donor could provide more routes to higher-quality solar cells.

Visible-Light-Promoted Palladium-Catalyzed Cross-Coupling of lodocarboranes with Disulfides and Phenylselenyl Chloride

This work describes a general method for the synthesis of a series of sulfenylated and selenylated carboranes at room temperature using readily available iodocarboranes as starting materials via boron-centered carboranyl radicals.Such hypervalent boron radicals are generated by a visible-light-promoted Pd(O)/Pd(I)pathway.They are useful intermediates and can be trapped by disulfides and phenylselenyl chloride for the convenient construction of B-S/Sebonds.

Atroposelective Synthesis of 2-Arylindoles via Chiral Phosphoric Acid-Catalyzed Direct Amination of Indoles

Indole-based atropisomers are a very important class of axially chiral compounds.However,the atroposelective synthesis of axially chiral 2-arylindole remains largely unexplored.In this study,we report the successful synthesis of atropisomeric 2-arylindoles using direct amination of indoles with p-quinonediimines in the presence of chiral phosphoric acid as a catalyst.Quinonediimine acts as an aminating reagent through formal polarity inversion of imine.The malonate group on the 2-aryl of 2-indoles was found to be essen-tial for high enantioselectivity of the products.This could be due to the additional interaction between the ester group and the cata-lyst,as well as the intramolecular hydrogen bonding.Our findings provide a new strategy for the asymmetric construction of 2-arylindole atropisomers.

Total synthesis of a putative yuzurimine-type Daphniphyllum alkaloid C_(14)–epi-deoxycalyciphylline H

One of the largest subfamilies within the famous Daphniphyllum alkaloid family is made up of the yuzurimine-type(or macrodaphniphyllamine-type) alkaloids. Their complex aza-polycyclic caged structures, several contiguous stereogenic centers, and vicinal all-carbon quaternary centers make these alkaloids formidable challenge for synthetic chemists. Recently, synthesis of these alkaloids has received extensive attention from our community. Herein, we wish to report the total synthesis of C_(14)–epideoxycalyciphylline H, a putative member of yuzurimine-type alkaloid subfamily. Key transformations employed in our approach include an intramolecular Prins reaction and a Pd-catalyzed enyne cycloisomerization. In addition, synthesis of a daphnezomine L-type alkaloid, paxdaphnidine A, was also studied.

Catalytic enantioselective N-silylation of sulfoximine

A rhodium/diphosphine-catalyzed asymmetric cross-dehydrogenative coupling between sulfoximines and dihydrosilanes has been achieved. This is the first report on the enantioselective N-silylation of sulfoximines. The protocol gives access to a variety of Si-stereogenic N-silylated sulfoximines in decent yield(up to 99%) with excellent stereoselectivity(up to 99%), featuring high atom economy, and a cleaner manner with H2as the sole byproduct. The obtained bis-Si-stereogenic monohydrosilane product can be further converted into the corresponding chiral polymer with pendant sulfoximine groups.

Strain-promoted S-arylation and alkenylation of sulfinamides using arynes and cyclic alkynes

The conversion of commercially available chiral sulfinamides into pharmaceutically useful chiral sulfoximines via direct SIVfunctionalization is synthetically attractive but challenging due to the competitive reaction of N-functionalization. Herein, we disclose a novel strain-release strategy to access stereospecific and chemoselective SIV-arylation and alkenylation of sulfinamides using arynes and strained cyclic alkynes. This method tolerates an unprecedented chemical diversity of functional groups attached to the nitrogen center(N-R). The origin of the high SIV-selectivity is elucidated by density functional theory calculations, suggesting a stepwise mechanism for the aryne substrates and a concerted mechanism for the cyclic alkynes.

Construction of a Metallacyclopentadiene Ring through the Attack of Carbanions to M≡C Bond Followed by C—H Activation

Metallacyclopentadienes are important metallacycles and regarded as intermediates in many reactions,therefore,new methods to achieve them are anticipated.In this study,a formal[3+2]method,through the reactions of an osmapentalyne with benzyl carbanions,was developed.The reactions underwent a nucleophilic attack of carbanions to the Os≡C bond,followed by C—H activation to form the five-membered osmacyclopentadiene ring.Most of the reactions were carried out at room temperature,the substituents on the aromatic rings of benzyl carbanions are diverse,and the resulting products contain an Os—H bond,representing a novel type of 10C-carbolong complexes.This work provides a new convenient route to construct metallacyclopentadienes,which is expected to further promote the development of such a type of substances.

Formic Acid Dehydrogenation for Hydrogen Production Promoted by Grubbs and Hoveyda-Grubbs Catalysts

In this work,we screened three Grubbs catalysts and two Hoveyda-Grubbs catalysts for the production of H_(2) by dehydrogenation of formic acid(FA).The best results were achieved with the use of a first-generation Hoveyda-Grubbs catalyst.With a catalyst loading of mere 0.5μmol, a maximum TON of 36356 was obtained within 3 h.Two key intermediates were identified by using 1H NMR and high-resolution electrospray ionization mass spectroscopy(HRESI-MS),based on which a mechanism possibly responsible for the observed catalysis was proposed.

Rapid Access to Free Phenols by Photocatalytic Acceptorless Dehydrogenation of Cyclohexanones at Room Temperature

Phenols are ubiquitous substructures in natural products and bioactive compounds.However,practical methods for the direct construction of phenols under mild conditions remain challenging.Herein,a photocatalytic acceptorless hydrogen-evolution aromatization of cyclohexanones or cyclohexenones at room temperature has been developed.The reaction features the visible-light and cobalt co-catalyzed sequential dehydrogenation of in-situ formed enol silyl ethers,which are regarded as a challenging process.This operationally simple method enables the synthesis of a series of phenols with diverse substitution patterns from cyclohexanones or cyclohexenones.Moreover,diverse substituted 1,2-,1,3-,and 1,4-benzenediols were obtained from cyclohexanediones,providing a general and straightforward method for the synthesis of phenols from simple starting materials under mild conditions.

Formal[2+1]Cycloadditions of a Metallacyclopentadiene Unit with Alkynes:Constructing Tetracyclic Conjugated Frameworks with Bridgehead Metals

Comprehensive Summary Metallacyclopentadienes play a vital role in transition-metal mediated and catalyzed cycloaddition reactions of alkynes.Though versatile reactions of metallacyclopentadienes with alkynes have been disclosed,[2+1]cycloadditions of metallacyclopentadienes and alkynes have never been discovered.In present work,we report the formal[2+1]cycloadditions of a metallacyclopentadiene unit with a broad scope of commercial alkynes,providing a facile strategy to construct tetracyclic conjugated compounds.The deuterated experiment indicates a metal vinylidene intermediate has been involved in[2+1]cycloaddition.Moreover,the electrophilic substitution reaction of the tetracyclic conjugated compound with the aid of density functional theory(DFT)calculated Fukui functions is investigated.

High energy density and superior charge/discharge efficiency polymer dielectrics enabled by rationally designed dipolar polarization

Although many dielectric polymers exhibit high energy storage density(Ue)with enhanced dipolar polarization at room temperature,the substantially increased electric conduction loss at high applied electric fields and high temperatures remains a great challenge.Here,we report a strategy that high contents of medium-polar ester group and end-group(St)modification are introduced into a biode-gradable polymer polylactic acid(PLA)to synergistically reduce the loss and enhance Ue and charge-discharge efficiency(h).The resultant St-modified PLA polymer(PLA-St)exhibits an Ue of 6.5 J/cm^(3)with an ultra-high h(95.4%),far outperforming the best reported dielectric polymers.It is worth noting that the modified molecular structures can generate deep trap centers and restrict the local dipole motions in the polymer,which are responsible for the reduction of conduction loss and improvements in high-temperature capacitive performance.In addition,the PLA-St polymer shows intrinsically excellent self-healing ability and cyclic stability surviving over 500000 charge-discharge cycles.This work offers an efficient route to next-generation eco-friendly dielectric polymers with high energy density,low loss,and long-term stability.

Crystallography,Packing Mode,and Aggregation State of Chlorinated Isomers for Efficient Organic Solar Cells

Revealing the molecular packing,intermolecular interactions,and aggregation behaviors in the nanocrystalline bulk heterojunction(BHJ)domains undertake the tasks for future materials design for efficient solar cells,especially in understanding the structure–property relationship of isomeric non-fullerene acceptors(NFAs).Theoretical calculations reveal that 2ClIC-βδ,withβ-andδ-chlorine-substituted terminal groups,achieves a relatively higher dipole moment for enhanced intermolecular interactions.More importantly,when comparing the single-crystal X-ray diffraction patterns of three isomeric NFAs,BTIC-BO4Cl-βδ,BTIC-BO4Cl-βγ,and BTIC-BO4Cl,the synergistic effect of chlorine atoms at theβ-andδ-positions endows BTIC-BO4Cl-βδbetter molecular planarity with a dihedral angle of 1.14°.In turn,this creates the shortestπ∙∙∙πdistance(3.28Å)and smallest binding energies(−51.66 kcal mol^(−1))of the three NFAs,resulting in the tightest three-dimensional network packing structure with a framework of L_(x)=14.0Åand L_(y)=13.6Å.Such a structure has multiple intermolecular interactions for better charge transfer.However,the chlorine atomat theγ-position in the other two isomers contributes to non-intermolecular interactions with subordinate packing arrangements.Subsequently,the red-shifted UV-absorption and higher electron mobility observed in neat films of BTIC-BO4Cl-βδagree well with its more ordered crystallinity.This leads to a more suitable fiber-like phase separation in the corresponding active blend,ultimately improving the device performance with superior charge transport.As a result,the highest power conversion efficiency of 17.04%with a current density of 26.07 mA cm^(−2)was obtained with the BTIC-BO4Cl-βδ-based device.The carrier dynamics test and grazing incidence wide-angle X-ray scattering measurement indicate that the packing arrangement of molecules in the nanocrystalline BHJ domains is consistent with their crystallinity.This work investigates the structure–property differences in three acceptors and emphasizes the effect of isomeric chlorine substitution,which suggests that changes in the crystal packing arrangement,especially the size of the framework,have a considerable influence on charge carrier transport and ultimately are reflected on the device efficiency elevation.

Pincer Ru with a single stereogenic identity for highly efficient asymmetric transfer hydrogenation of ketones

The asymmetric reduction of carbonyl compounds by means of the Ru-chiral diphosphine-chiral diamine catalysts is widely useful in organic synthesis where high levels of enantioselectivities have been attributed to multiple ligand chiral elements as well as essential stereochemical matching synergies within them.Described here is the design and discovery of new pincer-type Ru-catalysts that feature only single stereogenic element within ligands,yet the such significantly simplified structure is demonstrated to be well competent for effecting asymmetric reductions as well as kinetic resolutions over a broad range of highly functionalized ketones/alcohols,including heteroaryl substituted substrates that were challenging by known catalyst systems.Alcohols were furnished not only in excellent enantioselectivities,but with turnover numbers(up to 100,000 TONs)that reach the highest levels known to date in asymmetric transfer hydrogenation of ketones.This work should help shed light on the intricate origin of enantioselection in these important processes,and further stimulate rational understanding as well as optimization of chiral catalysts towards efficiency and simplicity.

Material and device design for organic solar cells: towards efficiency and stability

Organic solar cells(OSCs) have garnered significant attention as a novel photovoltaic technology and have been extensively investigated. In recent years, OSCs have made rapid strides in power conversion efficiency(PCE), demonstrating their significant potential in practical applications. In addition to high PCE, the practical application of OSCs demands a prolonged operating lifespan. The rational design of materials and devices to achieve efficient and stable OSCs is pivotal. This feature article presents a thorough analysis of our group's studies on enhancing efficiency and stability through material and device design. We introduce a range of exceptional chlorine-mediated organic photovoltaic materials and systematically summarize chlorine atom(Cl) induced effects on energy levels, molecular stacking, active layer film morphology and photovoltaic performance. Furthermore, the use of single-crystal diffraction technology allows for a comprehensive understanding of intermolecular packing and interaction at the molecular level. A series of highly efficient non-fullerene acceptors(NFAs) with threedimensional(3D) network packing structures are developed and discussed. Subsequently, based on efficient 3D network brominated NFAs, the studies on polymer and oligomer acceptor materials are carried out and achieve efficient and stable OSCs.In addition to materials design, the development of the “quasiplanar heterojunction”(Q-PHJ) based OSC device also plays an important role in achieving superior efficiency and stability. These design experiences of materials and devices hope to provide valuable guidance for the development of efficient and stable OSCs.

Nickel-catalyzed regioselective B(3,4,5,6)-H tetra-alkylation of o-carboranes

Though transition metal-catalyzed cage BH methylation has been well documented, catalytic alkylation of cage BH bonds remained elusive because transition metal alkyl complexes are prone to undergo β-H elimination. We report herein a highly efficient 8-aminoquinoline-assisted nickel-catalyzed regioselective cage B(3,4,5,6)-H tetra-alkylation of o-carboranes employing unactivated alkyl bromides as alkylating agents in the absence of any oxidants, leading to the preparation of a class of tetra-alkylated o-carboranes with a broad substrate scope in good to very high yields. This method opens new avenues for oxidant-free, direct, efficient, sustainable, and regioselective multiple B–H alkylation of carboranes via base metal catalysis.

Imidodiphosphorimidates (IDPis): Catalyst Motifs with Unprecedented Reactivity and Selectivity

The conceptually designed imidodiphosphorimidates(IDPis)have emerged as one of the most potent classes of chiral acid catalysts.They are characterized by enzyme-like,highly confined active site and high acidity,which underlie their wide-reaching applications as Bronsted acid catalysts and as precatalysts for silylium Lewis acids.Many carbon-carbon and carbon-heteroatom bond formation reactions that were deemed intractable could now be attained with spectacular reactivity and selectivity.Substrates that are small,unbiased and/or possess insufficient reactivity such as simple alkenes could now be engaged.The high structural confinement is particularly invaluable to control stereo-and chemoselectivity.The well-defined steric environment offers unique opportunity to control high-energy but structurally unbiased cation intermediates such as the norbonyl cations.Beyond practical appeals such as good scalability as well as ease and modularity of preparation,the extremely low pre-catalyst loadings required to achieve high turnover and stereoselectivity have also come to define a new frontier in organocatalysis.