Preparation of surface molecular imprinting fluorescent sensor based on magnetic porous silica for sensitive and selective determination of catechol.

A magnetic fluorescent molecularly imprinted sensor was successfully prepared and implemented to determine catechol (CT). Fe3O4 nanoparticles were synthesized by the solvothermal technique and mesoporous Fe3O4@SiO2@mSiO2 imprinted carriers were prepared by coating nonporous and mesoporous SiO2 shells on the surface of the Fe3O4 subsequently. The magnetic surface molecularly imprinted fluorescent sensor was created after the magnetic mesoporous carriers were modified with γ-methacryloxyl propyl trimethoxy silane to introduce double bonds on the surface of the carries and the polymerization was carried out in the presence of CT and fluorescent monomers. The magnetic mesoporous carriers were modified with γ-methacryloxyl propyl trimethoxy silane and double bonds were introduced on the surface of the carriers. After CT binding with the molecularly imprinted polymers (MIPs), the fluorescent intensity of the molecularly imprinted polymers (Ex = 400 nm, Em = 523 nm) increased significantly. The fluorescent intensity ratio (F/F0) of the sensor demonstrated a favorable linear correlation with the concentration of CT between 5 and 50 µM with a detection limit of 0.025 µM. Furthermore, the sensor was successfully applied to determine CT in actual samples with recoveries of 96.4-105% and relative standard deviations were lower than 3.5%. The results indicated that the research of our present work provided an efficient approach for swiftly and accurately determining organic pollutant in water.

A carbon nanosphere nanofluid for improving the toughness and thermal properties of epoxy composites.

A carbon nanosphere nanofluid (CNS-nanofluid) was successfully prepared through the non-covalent modification of carbon nanosphere (CNS) with the specific ionic liquid (i.e. [M2070][VBS]) at first. The resulting CNS-nanofluid is a homogeneous and stable fluid with liquid-like behaviour at room temperature, and which shows better dispersion stability in its good solvents and improved processability than the pristine CNS. Subsequently, this CNS-nanofluid was used as a kind of novel functional filler and incorporated into epoxy matrix to prepare the CNS-nanofluid filled epoxy composites (CNS-nanofluid/EP composites). The toughness and thermal properties of those CNS-nanofluid/EP composites were carefully characterized and analysed. And it was found that this CNS-nanofluid could respectively improve the impact toughness and glass transition temperature of the CNS-nanofluid/EP composites to 19.8 kJ m-2and 122.5 °C at the optimum amount, demonstrating that this CNS-nanofluid is a kind of promising functional filler to achieve robust epoxy composites, and thus opening up new possibilities with great significance for epoxy composites in high-performance applications.

Subtle Morphology Control with Binary Additives for High-Efficiency Non-Fullerene Acceptor Organic Solar Cells.

Adding an additive is one of the effective strategies to fine-tune active layer morphology and improve performance of organic solar cells. In this work, a binary additive 1,8-diiodooctane (DIO) and 2,6-dimethoxynaphthalene (DMON) to optimize the morphology of PBDB-T:TTC8-O1-4F-based devices is reported. With the binary additive, a power conversion efficiency (PCE) of 13.22% was achieved, which is higher than those of devices using DIO (12.05%) or DMON (11.19%) individually. Comparison studies demonstrate that DIO can induce the acceptor TTC8-O1-4F to form ordered packing, while DMON can inhibit excessive aggregation of the donor and acceptor. With the synergistic effect of these two additives, the PBDB-T:TTC8-O1-4F blend film with DIO and DMON exhibits a suitable phase separation and crystallite size, leading to a high short-circuit current density (Jsc) of 23.04 mA·cm-2 and a fill factor of 0.703 and thus improved PCE.

Highly Conducting MXene-Silver Nanowire Transparent Electrodes for Flexible Organic Solar Cells.

MXene, a new class of two-dimensional materials, offers a unique combination of metallic conductivity and hydrophilicity. This material has shown great promise in numerous applications including electromagnetic interference shielding, sensing, energy storage, and catalysis. In this paper, we report on the fabrication of transparent, conductive, and flexible MXene/silver nanowire (AgNW) hybrid films, resulting in the highest figure of merit (162.49) in the reported literature to date regarding an MXene-based transparent electrode. The hybrid films, prepared via a simple and scalable solution-processed method, exhibit good electrical conductivity, high transmittance, low roughness, work function matching, and robust mechanical performance. Following film fabrication, the hybrid electrodes were demonstrated to function as transparent electrodes in fullerene molecule PTB7-Th:PC71BM and nonfullerene molecule PBDB-T:ITIC organic photovoltaics (OPVs). In an effort to further improve the performance of flexible OPVs, a ternary structure of PBDB-T:ITIC:PC71BM was demonstrated, resulting in a power conversion efficiency (PCE) of 8.30%. Mechanical properties were also quantified, with the flexible ternary organic solar cells capable of retaining 84.6% of the original PCE after 1000 bending and unbending cycles to a 5 mm bending radius. These optoelectronic and mechanical performance metrics represent a breakthrough in the field of flexible optoelectronics.

A New Nonfullerene Acceptor with Near Infrared Absorption for High Performance Ternary-Blend Organic Solar Cells with Efficiency over 13.

A new acceptor-donor-acceptor (A-D-A) type nonfullerene acceptor, 3TT-FIC, which has three fused thieno[3,2-b]thiophene as the central core and difluoro substituted indanone as the end groups, is designed and synthesized. 3TT-FIC exhibits broad and strong absorption with extended onset absorption to 995 nm and a low optical bandgap of 1.25 eV. The binary device based on 3TT-FIC and the polymer PTB7-Th exhibits a power conversion efficiency (PCE) of 12.21% with a high short circuit current density (   Jsc) of 25.89 mA cm-2. To fine-tune the morphology and make full use of the visible region sunlight, phenyl-C71-butyricacid-methyl ester (PC71BM) is used as the third component to fabricate ternary devices. In contrast to the binary devices, the ternary blend organic solar cells show significantly enhanced EQE ranging from 300 to 700 nm and thus an improved  Jsc with a high value of 27.73 mA cm-2. A high PCE with a value of 13.54% is achieved for the ternary devices, which is one of the highest efficiencies in single junction organic solar cells reported to date. The results provide valuable insight for the ternary devices in which the external quantum efficiency (EQE) induced by the third component is evidently observed and directly contributed to the enhancement of the device efficiency.

Efficient carbazole-based small-molecule organic solar cells with an improved fill factor.

In this study, a new acceptor-donor-acceptor (A-D-A) small molecule, DI3TCz, with carbazole as the central unit and 1,3-indanedione as the end group, was designed and synthesized for application in organic solar cells. In contrast to the molecule DR3TCz with rhodanine as end groups, DI3TCz exhibited deep a LUMO energy level and a nearly unchanged HOMO energy level with a narrow optical band gap of 1.75 eV and red shifted absorption. Compared with DR3TCz, the DI3TCz device showed a PCE of 6.46% with a remaining high V oc value of 0.97 V, improved J sc of 10.40 mA cm-1 and a notable FF of 0.65, which is the highest PCE value reported to data for carbazole-based small molecules OPVs.

Fine-Tuning the Energy Levels of a Nonfullerene Small-Molecule Acceptor to Achieve a High Short-Circuit Current and a Power Conversion Efficiency over 12% in Organic Solar Cells.

Organic solar cell optimization requires careful balancing of current-voltage output of the materials system. Here, such optimization using ultrafast spectroscopy as a tool to optimize the material bandgap without altering ultrafast photophysics is reported. A new acceptor-donor-acceptor (A-D-A)-type small-molecule acceptor NCBDT is designed by modification of the D and A units of NFBDT. Compared to NFBDT, NCBDT exhibits upshifted highest occupied molecular orbital (HOMO) energy level mainly due to the additional octyl on the D unit and downshifted lowest unoccupied molecular orbital (LUMO) energy level due to the fluorination of A units. NCBDT has a low optical bandgap of 1.45 eV which extends the absorption range toward near-IR region, down to ≈860 nm. However, the 60 meV lowered LUMO level of NCBDT hardly changes the Voc level, and the elevation of the NCBDT HOMO does not have a substantial influence on the photophysics of the materials. Thus, for both NCBDT- and NFBDT-based systems, an unusually slow (≈400 ps) but ultimately efficient charge generation mediated by interfacial charge-pair states is observed, followed by effective charge extraction. As a result, the PBDB-T:NCBDT devices demonstrate an impressive power conversion efficiency over 12%-among the best for solution-processed organic solar cells.

Small-Molecule Acceptor Based on the Heptacyclic Benzodi(cyclopentadithiophene) Unit for Highly Efficient Nonfullerene Organic Solar Cells.

A new nonfullerene small molecule with acceptor-donor-acceptor (A-D-A) structure, namely, NFBDT, based on a heptacyclic benzodi(cyclopentadithiophene) (FBDT) unit using benzo[1,2-b:4,5-b']dithiophene as the core unit, was designed and synthesized. Its absorption ability, energy levels, thermal stability, as well as photovoltaic performances were fully investigated. NFBDT exhibits a low optical bandgap of 1.56 eV resulting in wide and efficient absorption that covered the range from 600 to 800 nm, and suitable energy levels as an electron acceptor. With the widely used and successful wide bandgap polymer PBDB-T selected as the electron donor material, an optimized PCE of 10.42% was obtained for the PBDB-T:NFBDT-based device with an outstanding short-circuit current density of 17.85 mA cm-2 under AM 1.5G irradiation (100 mW cm-2), which is so far among the highest performance of NF-OSC devices. These results demonstrate that the BDT unit could also be applied for designing NF-acceptors, and the fused-ring benzodi(cyclopentadithiophene) unit is a prospective block for designing new NF-acceptors with excellent performance.

A New Nonfullerene Electron Acceptor with a Ladder Type Backbone for High-Performance Organic Solar Cells.

Nonfullerene acceptor FDICTF (2,9-bis(2methylene-(3-(1,1-dicyanomethylene)indanone))-7,​12-​dihydro-​4,​4,​7,​7,​12,​12-​hexaoctyl-​4H-​cyclopenta[2″,​1″:5,​6;3″,​4″:5',​6']​diindeno[1,​2-​b:1',​2'-​b']dithiophene) modified by fusing the fluorene core in a precursor, yields 10.06% high power conversion efficiency, and demonstrates that the ladder and fused core backbone in A-D-A structure molecules is an effective design strategy for high-performance nonfullerene acceptors.

Evaluation of Small Molecules as Front Cell Donor Materials for High-Efficiency Tandem Solar Cells.

Three small molecules as front cell donors for tandem cells are thoroughly evaluated and a high power conversion efficiency of 11.47% is achieved, which demonstrates that the oligomer-like small molecules offer a good choice for high-performance tandem solar cells.

Subtle Balance Between Length Scale of Phase Separation and Domain Purification in Small-Molecule Bulk-Heterojunction Blends under Solvent Vapor Treatment.

A series of solvents with different solubilities for DR3TBDTT and PC71 BM, and different boiling points, is used for solvent vapor annealing (SVA) treatment to systematically investigate the solvent-morphology-performance relationship. The presence of solvent molecules inside bulk-heterojunction (BHJ) thin films promotes the mobility of both donor and acceptor molecules, leading to crystallization and aggregation, which are important in modulating morphology.

A solution-processed high performance organic solar cell using a small molecule with the thieno[3,2-b]thiophene central unit.

A solution processed acceptor-donor-acceptor (A-D-A) small molecule with thieno[3,2-b]thiophene as the central building block and 2-(1,1-dicyanomethylene)-rhodanine as the terminal unit, DRCN8TT, was designed and synthesized. The optimized power conversion efficiency (PCE) of 8.11% was achieved, which is much higher than that of its analogue molecule DRCN8T. The improved performance was ascribed to the morphology which consisted of small, highly crystalline domains that were nearly commensurate with the exiton diffusion length.

A series of simple oligomer-like small molecules based on oligothiophenes for solution-processed solar cells with high efficiency.

A series of acceptor-donor-acceptor simple oligomer-like small molecules based on oligothiophenes, namely, DRCN4T-DRCN9T, were designed and synthesized. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated. Except for DRCN4T, excellent performances were obtained for DRCN5T-DRCN9T. The devices based on DRCN5T, DRCN7T, and DRCN9T with axisymmetric chemical structures exhibit much higher short-circuit current densities than those based on DRCN6T and DRCN8T with centrosymmetric chemical structures, which is attributed to their well-developed fibrillar network with a feature size less than 20 nm. The devices based on DRCN5T/PC71BM showed a notable certified power conversion efficiency (PCE) of 10.10% under AM 1.5G irradiation (100 mW cm(-2)) using a simple solution spin-coating fabrication process. This is the highest PCE for single-junction small-molecule-based organic photovoltaics (OPVs) reported to date. DRCN5T is a rather simpler molecule compared with all of the other high-performance molecules in OPVs to date, and this might highlight its advantage in the future possible commercialization of OPVs. These results demonstrate that a fine and balanced modification/design of chemical structure can make significant performance differences and that the performance of solution-processed small-molecule-based solar cells can be comparable to or even surpass that of their polymer counterparts.

Solution-processed organic solar cells based on dialkylthiol-substituted benzodithiophene unit with efficiency near 10%.

A small molecule named DR3TSBDT with dialkylthiol-substituted benzo[1,2-b:4,5-b']dithiophene (BDT) as the central unit was designed and synthesized for solution-processed bulk-heterojunction solar cells. A notable power conversion efficiency of 9.95% (certified 9.938%) has been achieved under AM 1.5G irradiation (100 mW cm(-2)), with an average PCE of 9.60% based on 50 devices.

Synthesis and physical properties of the conjugated dendrons bearing twisted acenes used in solution processing of organic light-emitting diodes.

Five novel organic conjugated derivatives containing multifraction twisted acene units have been synthesized and characterized. These compounds and the model molecule 2-methyl-5,12-diphenyl-6:7,10:11-bisbenzotetracene emit strong blue light in diluted solution with quantum yields of 0.21-0.67, while in the solid state, except for the 1,2,3,4,5,6-hexa(2-(5,12-diphenyl-6:7,10:11-bis(4'-tert-butylbenzo)tetracene))benzene, green luminance is seen. The experimental results also indicate that the multifraction structure leads to a significant fluorescence enhancement (over two times) compared to the monomer, which might be attributed to the formation of delocalized excited state in multibranch structures. The quantum-chemical calculation implies that only two branches are involved in formation of the delocalized system for the multibranched derivatives. Furthermore, the organic light-emitting diode (OLED) devices using compounds 1,4-di(2-(5,12-diphenyl-6:7,10:11-bis(4'-tert-butylbenzo)tetracene))benzene, 1,3-di(2-(5,12-diphenyl-6:7,10:11-bis(4'-tert-butylbenzo)tetracene))benzene, and 1,3,5-tri(2-(5,12-diphenyl-6:7,10:11-bis(4'-tert-butylbenzo)tetracene))benzene as emitters exhibit good electroluminescent performance. Our systematic studies might provide more chances to challenge the rational design and synthesis of new- and high-generation branched dendrimers.