Halogenated Dibenzo[f,h]quinoxaline Units Constructed 2D-Conjugated Guest Acceptors for 19% Efficiency Organic Solar Cells.

Halogenation of Y-series small-molecule acceptors (Y-SMAs) is identified as an effective strategy to optimize photoelectric properties for achieving improved power-conversion-efficiencies (PCEs) in binary organic solar cells (OSCs). However, the effect of different halogenation in the 2D-structured large π-fused core of guest Y-SMAs on ternary OSCs has not yet been systematically studied. Herein, four 2D-conjugated Y-SMAs (X-QTP-4F, including halogen-free H-QTP-4F, chlorinated Cl-QTP-4F, brominated Br-QTP-4F, and iodinated I-QTP-4F) by attaching different halogens into 2D-conjugation extended dibenzo[f,h]quinoxaline core are developed. Among these X-QTP-4F, Cl-QTP-4F has a higher absorption coefficient, optimized molecular crystallinity and packing, suitable cascade energy levels, and complementary absorption with PM6:L8-BO host. Moreover, among ternary PM6:L8-BO:X-QTP-4F blends, PM6:L8-BO:Cl-QTP-4F obtains a more uniform and size-suitable fibrillary network morphology, improved molecular crystallinity and packing, as well as optimized vertical phase distribution, thus boosting charge generation, transport, extraction, and suppressing energy loss of OSCs. Consequently, the PM6:L8-BO:Cl-QTP-4F-based OSCs achieve a 19.0% efficiency, which is among the state-of-the-art OSCs based on 2D-conjugated Y-SMAs and superior to these devices based on PM6:L8-BO host (17.70%) and with guests of H-QTP-4F (18.23%), Br-QTP-4F (18.39%), and I-QTP-4F (17.62%). The work indicates that halogenation in 2D-structured dibenzo[f,h]quinoxaline core of Y-SMAs guests is a promising strategy to gain efficient ternary OSCs.

Non-Fully Conjugated Dimerized Giant Acceptors with Different Alkyl-Linked Sites for Stable and 19.13 % Efficiency Organic Solar Cells.

Achieving both high power conversion efficiency (PCE) and device stability is a major challenge for the practical development of organic solar cells (OSCs). Herein, three non-fully conjugated dimerized giant acceptors (named 2Y-sites, including wing-site-linked 2Y-wing, core-site-linked 2Y-core, and end-site-linked 2Y-end) are developed. They share the similar monomer precursors but have different alkyl-linked sites, offering the fine-tuned molecular absorption, packing, glass transition temperature, and carrier mobility. Among their binary active layers, D18/2Y-wing has better miscibility, leading to optimized morphology and more efficient charge transfer compared to D18/2Y-core and D18/2Y-end. Therefore, the D18/2Y-wing-based OSCs achieve a superior PCE of 17.73 %, attributed to enhanced photocurrent and fill factor. Furthermore, the D18/2Y-wing-based OSCs exhibit a balance of high PCE and improved stability, distinguishing them within the 2Y-sites. Building on the success of 2Y-wing in binary systems, we extend its application to ternary OSCs by pairing it with the near-infrared absorbing D18/BS3TSe-4F host. Thanks to the complementary absorption within 300-970 nm and further optimized morphology, ternary OSCs obtain a higher PCE of 19.13 %, setting a new efficiency benchmark for the dimer-derived OSCs. This approach of alkyl-linked site engineering for constructing dimerized giant acceptors presents a promising pathway to improve both PCE and stability of OSCs.

Green-Solvent Processed Blade-Coating Organic Solar Cells with an Efficiency Approaching 19% Enabled by Alkyl-Tailored Acceptors.

Power-conversion-efficiencies (PCEs) of organic solar cells (OSCs) in laboratory, normally processed by spin-coating technology with toxic halogenated solvents, have reached over 19%. However, there is usually a marked PCE drop when the blade-coating and/or green-solvents toward large-scale printing are used instead, which hampers the practical development of OSCs. Here, a new series of N-alkyl-tailored small molecule acceptors named YR-SeNF with a same molecular main backbone are developed by combining selenium-fused central-core and naphthalene-fused end-group. Thanks to the N-alkyl engineering, NIR-absorbing YR-SeNF series show different crystallinity, packing patterns, and miscibility with polymeric donor. The studies exhibit that the molecular packing, crystallinity, and vertical distribution of active layer morphologies are well optimized by introducing newly designed guest acceptor associated with tailored N-alkyl chains, providing the improved charge transfer dynamics and stability for the PM6:L8-BO:YR-SeNF-based OSCs. As a result, a record-high PCE approaching 19% is achieved in the blade-coating OSCs fabricated from a green-solvent o-xylene with high-boiling point. Notably, ternary OSCs offer robust operating stability under maximum-power-point tracking and well-keep > 80% of the initial PCEs for even over 400 h. Our alkyl-tailored guest acceptor strategy provides a unique approach to develop green-solvent and blade-coating processed high-efficiency and operating stable OSCs, which paves a way for industrial development.

Unidirectional Sidechain Engineering to Construct Dual-Asymmetric Acceptors for 19.23 % Efficiency Organic Solar Cells with Low Energy Loss and Efficient Charge Transfer.

Achieving both high open-circuit voltage (Voc ) and short-circuit current density (Jsc ) to boost power-conversion efficiency (PCE) is a major challenge for organic solar cells (OSCs), wherein high energy loss (Eloss ) and inefficient charge transfer usually take place. Here, three new Y-series acceptors of mono-asymmetric asy-YC11 and dual-asymmetric bi-asy-YC9 and bi-asy-YC12 are developed. They share the same asymmetric D1 AD2 (D1 =thieno[3,2-b]thiophene and D2 =selenopheno[3,2-b]thiophene) fused-core but have different unidirectional sidechain on D1 side, allowing fine-tuned molecular properties, such as intermolecular interaction, packing pattern, and crystallinity. Among the binary blends, the PM6 : bi-asy-YC12 one has better morphology with appropriate phase separation and higher order packing than the PM6 : asy-YC9 and PM6 : bi-asy-YC11 ones. Therefore, the PM6 : bi-asy-YC12-based OSCs offer a higher PCE of 17.16 % with both high Voc and Jsc , due to the reduced Eloss and efficient charge transfer properties. Inspired by the high Voc and strong NIR-absorption, bi-asy-YC12 is introduced into efficient binary PM6 : L8-BO to construct ternary OSCs. Thanks to the broadened absorption, optimized morphology, and furtherly minimized Eloss , the PM6 : L8-BO : bi-asy-YC12-based OSCs achieve a champion PCE of 19.23 %, which is one of the highest efficiencies among these annealing-free devices. Our developed unidirectional sidechain engineering for constructing bi-asymmetric Y-series acceptors provides an approach to boost PCE of OSCs.

Regioisomer-Free Difluoro-Monochloro Terminal-based Hexa-Halogenated Acceptor with Optimized Crystal Packing for Efficient Binary Organic Solar Cells.

Herein, we synthesized new hetero-halogenated end groups with well-determined fluorinated and chlorinated substitutions (o-FCl-IC and FClF-IC), and synthesized regioisomer-free small molecular acceptors (SMAs) Y-Cl, Y-FCl, and Y-FClF with distinct hetero-halogenated terminals, respectively. The single-crystal structures and theoretical calculations indicate that Y-FClF exhibits more compact three-dimensional network packing and more significant π-π electronic coupling compared to Y-FCl. From Y-Cl to Y-FCl to Y-FClF, the neat films exhibit a narrower optical band gap and gradually enhanced electron mobility and crystallinity. The PM6 : Y-FClF blend film exhibits the strongest crystallinity with preferential face-on molecular packing, desirable fibrous morphology with suitable phase segregation, and the highest and balanced charge mobilities among three blend films. Overall, the PM6 : Y-FClF organic solar cells (OSCs) deliver a remarkable efficiency of 17.65 %, outperforming the PM6 : Y-FCl and PM6 : Y-Cl, which is the best PCE for reported hetero-halogens-based SMAs in binary OSCs. Our results demonstrate that difluoro-monochloro hetero-terminal is a superior regio-regular unit for enhancing the intermolecular crystal packing and photovoltaic performance of hetero-halogenated SMAs.

Boosting Energy Storage Performance of Lead-Free Ceramics via Layered Structure Optimization Strategy.

Owing to the current global scenario of environmental pollution and the energy crisis, the development of new dielectrics using lead-free ceramics for application in advanced electronic and energy storage systems is essential because of the high power density and excellent stability of such ceramics. Unfortunately, most of them have low breakdown strength and/or low maximum polarization, resulting in low energy density and efficiency. To overcome this limitation here, lead-free ceramics comprising a layered structure are designed and fabricated. By optimizing the distribution of the layered structure, a large maximum polarization and high applied electric field (>500 kV cm-1 ) can be achieved; these result in an ultrahigh recoverable energy storage density (≈7 J cm-3 ) and near ideal energy storage efficiency (≈95%). Furthermore, the energy storage performance without obvious deterioration over a broad range of operating frequencies (1-100 Hz), working temperatures (30-160 °C), and fatigue cycles (1-104 ). In addition, the prepared ceramics exhibit extremely high discharge energy density (4.52 J cm-3 ) and power density (405.50 MW cm-3 ). Here, the results demonstrate that the strategy of layered structure design and optimization is promising for enhancing the energy storage performance of lead-free ceramics.

Tunable Domain Switching Features of Incommensurate Antiferroelectric Ceramics Realizing Excellent Energy Storage Properties.

An incommensurate modulated antiferroelectric phase is a key part of ideal candidate materials for the next generation of dielectric ceramics with excellent energy storage properties. However, there is less research carried out when considering its relatively low polarization response. Here, the incommensurate phase is modulated by stabilizing the antiferroelectric phase and the energy storage performance of the incommensurate phase under ultrahigh electric field is studied. The tape-casting method is applied to construct dense and thin ceramics. La3+ doping induces a room-temperature incommensurate antiferroelectric orthorhombic matrix. With little Cd2+ , the extremely superior energy storage performances arose as follows: when 0.03, the recoverable energy storage density reaches ≈19.3 J cm-3 , accompanying an ultrahigh energy storage efficiency of ≈91% (870 kV cm-1 ); also, a giant discharge energy density of ≈15.4 J cm-3 emerges during actual operation. In situ observations demonstrate that these superior energy storage properties originate from the phase transition from the incommensurate antiferroelectric orthorhombic phase to the induced rhombohedral relaxor ferroelectric one. The adjustable incommensurate period affects the depolarization response. The revealed phase-transition mechanism enriches the existing antiferroelectric-ferroelectric transition. Attention to the incommensurate phase can provide a reference for the selection of the next generation of high-performance antiferroelectric materials.

Two-Dimensional Fillers Induced Superior Electrostatic Energy Storage Performance in Trilayered Architecture Nanocomposites.

Dielectric capacitors with ultrahigh power densities and fast charging/discharging rates are of vital relevance in advanced electronic markets. Nevertheless, a tradeoff always exists between breakdown strength and polarization, which are two essential elements determining the energy storage density. Herein, a novel trilayered architecture composite film, which combines outer layers of two-dimensional (2D) BNNS/poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) with high breakdown strength and an intermediate layer made of blended 2D MoS2 nanosheets/P(VDF-HFP) with large polarization, is fabricated using the layer-by-layer casting method. The insulating BNNS with a wide band gap is able to largely alleviate the distortion of the local electric field, thereby suppressing the leakage current and effectively reducing the conductivity loss, while the 2D MoS2 nanosheets act as microcapacitors in the polymer composites, thus significantly increasing the permittivity. A finite element simulation is carried out to further analyze the evolution process of electrical treeing in the experimental breakdown of the polymer nanocomposites. Consequently, the nanocomposites possess an excellent discharged energy density of 25.03 J/cm3 accompanied with a high charging/discharging efficiency of 77.4% at 650 MV/m, which greatly exceeds those of most conventional single-layer films. In addition, the corresponding composites exhibit an outstanding reliability of energy storage performance under continuous cycling. The excellent performances of these polymer-based nanocomposite films could pave a way for widespread applications in advanced capacitors.

Morphotropic Relaxor Boundary Construction Highly Boosts the Piezoelectric Properties of Bi-Based Lead-Free Thin Films.

To achieve large electrostrain and low hysteresis, we further optimized a morphotropic phase boundary (MPB) by modulating its local polar symmetries. The construction of a morphotropic relaxor boundary (MRB) in thin films can be achieved by suitable introduction of Bi(Fe0.95Mn0.03Ti0.02)O3 into (Bi0.5Na0.5)TiO3-SrTiO3 to form a solid solution. The designed thin film achieves surprising piezoelectric properties with an inverse piezoelectric coefficient of 179.7 pm V-1 and negligible hysteresis. The composition of two relaxors with different local polar symmetries (tetragonal nanoregions and rhombohedral nanoregions), namely, an MRB, and the coexistence of multiscale domain structures can greatly weaken the anisotropy of polarization, degrade the energy barrier, attenuate the discontinuity of polarization, and achieve a large electrostrain and low hysteresis. The domain dynamics of the PNRs under the action of an external excitation field are analyzed to clarify the enhancement mechanism. This construction of MRBs is feasible for producing lead-free piezoelectric films with high-voltage electrical properties and low hysteresis, and various experimental design and theoretical references are provided.

Composition and Structure Optimized BiFeO3 -SrTiO3 Lead-Free Ceramics with Ultrahigh Energy Storage Performance.

Dielectric ceramic capacitors have attracted increasing attention as advanced pulsed power devices and modern electronic systems owing to their fast charge/discharge speed and high power density. However, it is challenging to meet the urgent needs of lead-free ceramics with superior energy storage performance in practical applications. Herein, a strategy for the composition and structural modification is proposed to overcome the current challenge. The lead-free ceramics composed of BiFeO3 -SrTiO3 are fabricated. A low hysteresis and high polarization can be achieved via composition optimization. The experimental results and finite element simulations indicate that the two-step sintering method significantly influences the decrease in the grain size and improvement in the breakdown strength (EBDS ). A high EBDS of ≈750 kV cm-1 accompanied by a large maximum polarization (≈40 µC cm-2 ) and negligible remanent polarization (<2 µC cm-2 ) contribute to the ultrahigh energy density and efficiency values of the order of 8.4 J cm-3 and ≈90%, respectively. Both energy density and efficiency exhibit excellent stability over the frequency range of 1-100 Hz and temperatures up to 120 °C, along with the superior power density of 280 MW cm-3 , making the studied BiFeO3 -SrTiO3 ceramics potentially useful for high-power energy storage applications.

Modulating Crystal Packing, Film Morphology, and Photovoltaic Performance of Selenophene-Containing Acceptors through a Combination of Skeleton Isomeric and Regioisomeric Strategies.

Here, we report a series of acceptor-donor-acceptor (A-D-A) architecture isomeric acceptors (SeCT-IC, CSeT-IC, and CTSe-IC), which have an identical electron-deficient terminal A-group and three different central D-cores with the selenophene at the innermost, relatively outer, and outermost positions of the central core, respectively. From CSeT-IC to the atom regioisomer of CTSe-IC and to the conjugated skeleton isomer of SeCT-IC, the optical band gap of neat films continuously reduced and highest occupied molecular orbitals (HOMO) gradually upshifted with changing the selenophene from relatively outer position to the outermost position and to the innermost position of the central core. More importantly, the single-crystal structure and the GIWAXS measurements revealed that CTSe-IC presents the closest π-π stacking distance, the largest CCL, and the best molecular order and crystallinity, which led to the highest electron mobility in neat films. Furthermore, the J71:CTSe-IC blend film presents a more ordered film morphology with more proper phase separation domain size, more dominant face-on orientation, and relatively higher and more balanced electron-hole mobilities in comparison with that of J71:SeCT-IC and J71:CSeT-IC. Consequently, the J71:CTSe-IC-based organic solar cell gave a superior power conversion efficiency (PCE) of 11.59%, which was obviously higher than those for J71:SeCT-IC (10.89%) and J71:CSeT-IC (8.52%). Our results demonstrate that the acceptor with selenophene in the outermost position led to significantly enhance the PCE. More importantly, rational modulation of the central fused core in combination with the conjugated skeleton isomeric method and the atom regioisomeric method provides an effective way to understand the structure-crystallinity-photovoltaic property relationship of selenophene-based regioisomers.

Two-Dimensional Conjugated Benzo[1,2-b:4,5-b']diselenophene-Based Copolymer Donor Enables Large Open-Circuit Voltage and High Efficiency in Selenophene-based Organic Solar Cells.

A two-dimensional electron-rich fused-ring moiety (ClBDSe) based on benzo[1,2-b:4,5-b']diselenophene is synthesized. Three copolymers (PBDT-Se, PBDSe-T, and PBDSe-Se) are obtained by manipulating the connection types and number of selenophene units on the conjugated main chains with two 2D fused-ring units and two different π-bridges, respectively. In comparison with PBDT-Se and PBDSe-Se, PBDSe-T with benzo[1,2-b:4,5-b']diselenophene unit and thiophene π-bridge exhibits the deepest HOMO energy level and the strongest crystallinity in neat films. The PBDSe-T:Y6 blend film exhibits the best absorption complementarity, the most distinctive face-on orientation with proper phase separation, the highest carrier mobilities, and the lowest charge recombination among three blend films. Finally, the PBDSe-T:Y6-based device delivers an impressive power conversion efficiency (PCE) of 14.50 %, which is higher than those of PBDT-Se:Y6 and PBDSe-Se:Y6. Moreover, a decent open-circuit voltage (Voc ) of 0.89 V with a remarkably small energy loss of 0.44 eV is achieved for PBDSe-T:Y6. The efficiency of 14.50 % is the highest value for selenophene-containing copolymer-based binary organic solar cells (OSCs). This study provides evidence that introduction of 2D-benzo[1,2-b:4,5-b']diselenophene as a fused electron-rich unit with π-bridging into copolymeric donors is a valid strategy for providing high Voc and excellent PCE simultaneously in selenophene-based OSCs.

A Synergistic Strategy of Manipulating the Number of Selenophene Units and Dissymmetric Central Core of Small Molecular Acceptors Enables Polymer Solar Cells with 17.5 % Efficiency.

A dissymmetric backbone and selenophene substitution on the central core was used for the synthesis of symmetric or dissymmetric A-DA'D-A type non-fullerene small molecular acceptors (NF-SMAs) with different numbers of selenophene. From S-YSS-Cl to A-WSSe-Cl and to S-WSeSe-Cl, a gradually red-shifted absorption and a gradually larger electron mobility and crystallinity in neat thin film was observed. A-WSSe-Cl and S-WSeSe-Cl exhibit stronger and tighter intermolecular π-π stacking interactions, extra S⋅⋅⋅N non-covalent intermolecular interactions from central benzothiadiazole, better ordered 3D interpenetrating charge-transfer networks in comparison with thiophene-based S-YSS-Cl. The dissymmetric A-WSSe-Cl-based device has a PCE of 17.51 %, which is the highest value for selenophene-based NF-SMAs in binary polymer solar cells. The combination of dissymmetric core and precise replacement of selenophene on the central core is effective to improve Jsc and FF without sacrificing Voc .

Achieving Superior Energy Storage Properties and Ultrafast Discharge Speed in Environment-Friendly Niobate-Based Glass Ceramics.

Glass ceramics composed of Na2O-BaO-Bi2O3-Nb2O5-Al2O3-SiO2 (NBBN-AS) were modified by rare-earth doping and prepared via the melt-quenching process accompanied by controlled crystallization. High-resolution transmission electron microscopy displayed the glassy matrix closely encompassing the nanosized NaNbO3, Ba2NaNb5O15, BaAl2Si2O8, and AlNbO4 crystalline grains. With rare-earth doping, the NBBN-AS glass ceramics' theoretical energy storage density can reach 22.48 J/cm3. This excellent energy storage property is credited with increasing breakdown strength, and numerical simulation was applied to reveal the intrinsic mechanism for increased breakdown strength by rare-earth doping. The charge-discharge results indicated a giant power density of 220 MW/cm3 as well as an ultrafast discharge speed of 11 ns. The results indicate that the glass ceramic can be used in advanced capacitor applications.

Enhanced piezoelectric properties of (1 -x)BiFe0.98(Zn0.5Hf0.5)0.02O3-xBaTiO3 ceramics near the morphotropic phase boundary.

Here, (1 -x)BiFe0.98(Zn0.5Hf0.5)0.02O3-xBaTiO3 + 1 mol% MnO2 (x = 0.225, 0.250, 0.265, 0.275, 0.285, and 0.300) (BFZH-xBT) ceramics were synthesized using a traditional ceramic sintering technique. A morphotropic phase boundary (MPB) consisting of rhombohedral (R) and tetragonal (T) phases was formed in the BFZH-xBT ceramics when x = 0.285. The suitable content of BT was conducive to enlarge the particle size, improve ferroelectric and piezoelectric properties, and reduce the leakage current density. For the optimal component at x = 0.285, we observed the largest grain size, a lowest leakage current density value of ∼1.93 × 10-5 A cm-2, minimum content of oxygen vacancies, high temperature of 478 °C and the highest piezoelectric coefficient (d33) of 130 pC N-1.

Construction of Fully Substituted 2-Pyridone Derivatives via Four-Component Branched Domino Reaction Utilizing Microwave Irradiation.

Microwave irradiation, four-component branched domino reaction of methyl acetoacetate/2,4-pentanedione, diethyl malonate, triethyl orthoformate and amines offering an extremely efficient strategy for the construction of fully substituted 2-pyridone derivatives under sustainable conditions is established. This self-sorting branched domino transformation is proposed to proceed separate through N-nucleophilic addition and imine-enamine tautomerization/condensation reaction generated from enamino ester and diethyl ethoxymethylenemalonate, and then would be subjected to an aza-ene reaction and intramolecular cyclization mechanism to afford the 2-pyridones with only water and ethanol as byproducts. The simple experimental procedure, high bond-forming efficiency, step and atom economy, inexpensive readily available starting materials, moderate to excellent yields, and good functional group compatibility are other noteworthy advantages of this method.

Three-Component One-Pot Approach to Highly Efficient and Sustainable Synthesis of the Functionalized Quinolones via Linear/Branched Domino Protocols, Key Synthetic Methods for the Floxacin of Quinolone Drugs.

The development of a clear chemical process to produce diverse value-added chemicals from low-cost raw materials is a particularly attractive concept and represents a considerable challenge in sustainable organic synthesis. Herein, two highly efficient and clear methods for the synthesis of quinolone derivatives based on a linear/branched domino protocol under sustainable conditions were established. The main advantages of these protocols are the simple experimental procedure, high bond-forming efficiency, inexpensive readily available starting materials, moderate to excellent yields with good functional group compatibility, and nonchromatographic purification, which render these methods particularly attractive for the sustainable preparation of biologically and medicinally interesting molecules. To demonstrate the practical utility of our protocol, existing pharmaceutical sarafloxacin was successfully synthesized. Furthermore, a postulated reaction pathway including condensation reaction/nucleophilic aromatic substitution/Friedel-Crafts reaction for these domino reactions is also discussed.