A Multifluorination Strategy Toward Wide Bandgap Polymers for Highly Efficient Organic Solar Cells.

Creating new electron-deficient unit is highly demanded to develop high-performance polymer donors for non-fullerene organic solar cells (OSCs). Herein, we reported a multifluorinated unit 4,5,6,7-tetrafluoronaphtho[2,1-b : 3,4-b']dithio-phene (FNT) and its polymers PFNT-F and PFNT-Cl. The advantages of multifluorination: (1) it enables the polymers to exhibit low-lying HOMO (≈-5.5 eV) and wide band gap (≈2.0 eV); (2) the short interactions (F⋅⋅⋅H, F⋅⋅⋅F) endow the polymers with properties of high film crystallinity and efficient hole transport; (3) well miscibility with NFAs that leads to a more well-defined nanofibrous morphology and face-on orientation in the blend films. Therefore, the PFNT-F/Cl : N3 based OSCs exhibit impressive FF values of 0.80, and remarkable PCEs of 17.53 % and 18.10 %, which make them ranked the best donor materials in OSCs. This work offers new insights into the rational design of high-performance polymers by multifluorination strategy.

Syntheses and properties of nine-ring-fused linear thienoacenes.

π-Extended nine-ring-fused linear thienoacenes 1a­c with internal thieno[3,2-b;4,5-b']dithiophene substructures were synthesized. Their optical and electrochemical properties were investigated. Thin-film transistor characteristics showed all compounds displayed high device reproducibility and nearly no dependence on substrate temperatures. The highest performance was observed for 1c-based devices with mobility up to 1.0 cm2/Vs and current on/off ratio of 10(7), whereas the maximum mobility was 0.5 cm2/Vs for 1b and 0.011 cm2/Vs for 1a.

Wet-spinning fluorescent alginate fibres achieved by doping PEI modified CPDs for multiple anti-counterfeiting.

Carbonized polymer dots (CPDs) with satisfactory excitation-dependent-emission and biocompatibility had great potential in anti-counterfeiting fibres field. However, it was difficult for CPDs to combined into the fibres due to the unstable interaction between CPDs and spinnable polymer matrix. Polyethyleneimine (PEI) was used to modify CPDs (namely PEI-CPDs) for achieving stable interactions with sodium alginate (SA) by a simple method, which including the physical interaction between the amino groups of PEI-CPDs and carboxyl groups of SA and the chain entanglement between two types of polymer chains. Then alginate fibres based on PEI-CPDs (PEI-CPDs/CaALG fibres) were successfully prepared by wet-spinning for the first time with less loss of PEI-CPDs. The high mechanical strength, excellent thermal stability and good biocompatibility achieved by PEI-CPDs/CaALG fibres. Furthermore, the fibres exhibited the excitation-dependent-emission property. Anti-counterfeiting of the fibres was conducted on both textile and papers, which showed higher security than the existing anti-counterfeiting fibres.

Highly ordered thin films of 5,5''-bis(3'-fluoro-biphenyl-4-yl)-2,2' : 5',2''-terthiophene with two meso-phases.

The growth process and phase state of 5,5''-bis(3'-fluoro-biphenyl-4-yl)-2,2' : 5',2''- terthiophene (m-F2BP3T) thin films were investigated by atomic force microscopy (AFM), in-plane and out-of-plane X-ray diffraction (XRD), and selected area electron diffraction (SAED). Two meso-phases (thin film phases) of m-F2BP3T films on SiO(2) surface were obtained in the early stages. The m-F2BP3T films initially exhibited two-dimensional (2D) layers (≤4 ML) followed by three-dimensional (3D) island growth. The film structure evolved two thin film phases in the first four layers and the bulk phase was formed from the fifth layer, which occurred concomitantly with the change of the growth mode. Moreover, the variation of weak epitaxy growth behavior of ZnPc from 2D to 3D growth further reflects that the phase state of the first three layers is different from that of the fourth layer, in spite of ZnPc crystals showing just one orientation corresponding to commensurate epitaxy. The novel phase behavior is closely related to the synergistic effects of the outstanding soft matter properties, limited elasticity of organic molecules, and strain originating from the SiO(2) substrate. This study investigates novel phase behavior in organic thin films and provides significant insight into the mechanism of the phase transition.

Visual Detection of COVID-19 from Materials Aspect.

Abstract: In the recent COVID-19 pandemic, World Health Organization emphasized that early detection is an effective strategy to reduce the spread of SARS-CoV-2 viruses. Several diagnostic methods, such as reverse transcription-polymerase chain reaction (RT-PCR) and lateral flow immunoassay (LFIA), have been applied based on the mechanism of specific recognition and binding of the probes to viruses or viral antigens. Although the remarkable progress, these methods still suffer from inadequate cellular materials or errors in the detection and sampling procedure of nasopharyngeal/oropharyngeal swab collection. Therefore, developing accurate, ultrafast, and visualized detection calls for more advanced materials and technology urgently to fight against the epidemic. In this review, we first summarize the current methodologies for SARS-CoV-2 diagnosis. Then, recent representative examples are introduced based on various output signals (e.g., colorimetric, fluorometric, electronic, acoustic). Finally, we discuss the limitations of the methods and provide our perspectives on priorities for future test development.

1,3,5-Triazine and dibenzo[b,d]thiophene sulfone based conjugated porous polymers for highly efficient photocatalytic hydrogen evolution.

Organic conjugated porous polymers, triazine-Ph-CPP and triazine-Th-CPP, are synthesized and characterized. Without further addition of co-catalysts, triazine-Ph-CPP exhibits a HER of 16 287 µmol g-1 h-1 and an apparent quantum yield of 61.5% at 365 nm, which demonstrates that the dibenzo[b,d]thiophene sulfone and 1,3,5-triazine based polymer is a unique prototype of a highly efficient hydrogen evolution photocatalyst.

Fluorine-substituted quinoidal thiophene with a F-H hydrogen bond locked conformation for high-performance n-channel organic transistors.

The novel dicyanomethylene-substituted 1,2-bis(thieno[3,2-b]thiophene-2-yl)ethene based quinoidal compounds QBTTE and F2-QBTTE are reported. The FH (vinylene) hydrogen bonds lock the backbone conformation and greatly improve the transistor performance of F2-QBTTE.

Modulating Surface Morphology and Thin-Film Transistor Performance of Bi-thieno[3,4-c]pyrrole-4,6-dione-Based Polymer Semiconductor by Altering Preaggregation in Solution.

Due to their strong intermolecular interactions, polymer semiconductors aggregate in solution even at elevated temperature. With the aim to study the effect of this kind preaggregation on the order of thin films and further transistor performance, bi-thieno[3,4-c]pyrrole-4,6-dione and fluorinated oligothiophene copolymerized polymer semiconductor P1, which shows strong temperature-dependent aggregation behavior in solution, is synthesized. Its films are deposited through a temperature-controlled dip-coating technique. X-ray diffraction and atomic force microscopy results reveal that the aggregation behavior of P1 in solution affects the microstructures and order of P1 films. The charge transport properties of P1 films are investigated with bottom-gate top-contacted thin-film transistors. The variation of device performance (from 0.014  to 1.03 cm2 V-1 s-1) demonstrates the importance of optimizing preaggregation degree. The correlation between preaggregation degree and transistor performance of P1 films is explored.

Cu-Thienoquinone Charge-Transfer Complex: Synthesis, Characterization, and Application in Organic Transistors.

A facile and unusual reaction between thienoquinone compound QDTBDT2C and copper is reported. The formation of Cu-QDTBDT2C complex is proved by absorption spectra, IR spectra, Raman spectra, and X-ray photoelectron spectroscopy data. This complex can serve as a doping layer at the interface of Cu/QDTBDT2C and greatly improve the performance of organic transistors in which the copper electrode is source/drain electrodes and QDTBDT2C is an active layer. The transistors display an electron mobility of 0.95 cm2 V-1 s-1, to our knowledge, the highest electron mobility reported for copper electrode-based n-type transistors and nearly two times higher than that of the Au electrode-based devices. These results demonstrate the potential applications of Cu-QDTBDT2C complex in organic electronics, and the unique properties of QDTBDT2C (spontaneously reacting with copper) provide a new insight into the design of n-type organic semiconductors for copper electrode-based organic transistors.

Diacenaphthylene-fused benzo[1,2-b:4,5-b']dithiophenes: polycyclic heteroacenes containing full-carbon five-membered aromatic rings.

We herein report on an efficient synthesis of diacenaphthylene-fused benzo[1,2-b:4,5-b']dithiophenes and demonstrate that their packing structure in the solid state depends on the substituent groups. These compounds form dimers with their radical cations in high concentration solution and exhibit good field-effect mobility.

Bithienopyrroledione vs. thienopyrroledione based copolymers: dramatic increase of power conversion efficiency in bulk heterojunction solar cells.

Bithienopyrroledione (bi-TPD) based polymers P1 and P2 are designed and synthesized. Photovoltaic devices based on P1:PC71BM and P2:PC71BM blend films show power conversion efficiencies (PCEs) of 8.22% and 9.08%, respectively, whereas devices based on their thienopyrroledione (TPD)-based analogue P3 and PC71BM blend films display a PCE of 5.10%.

A Furan-Thiophene-Based Quinoidal Compound: A New Class of Solution-Processable High-Performance n-Type Organic Semiconductor.

The furan-thiophene-based quinoidal organic semiconductor, TFT-CN, is designed and synthesized. TFT-CN displays a high electron mobility of 7.7 cm(2) V(-1) s(-1) , two orders of magnitude higher than the corresponding thiophene-based derivative.

Synthesis, structure, and opto-electronic properties of regioisomeric pyrene-thienoacenes.

Three regioisomeric sulfur-bridged pyrene-thienoacenes (PTAs) have been synthesized. The crystal structures and optoelectronic properties of these ring-fused PTAs and their ring-opened precursors have been fully investigated. Among these isomers, the [3,4]-extended compound (4-S-PTA) shows the most pronounced spectral red-shift and highest quantum yield as well as large transistor mobility.

Donor-acceptor-donor type organic semiconductor containing quinoidal benzo[1,2-b:4,5-b']dithiophene for high performance n-channel field-effect transistors.

A donor-acceptor-donor (D-A-D) type small molecule , with dicyano-substituted quinoidal benzo[1,2-b:4,5-b']dithiophene as the acceptor, was designed and synthesized. A high electron mobility up to 0.88 cm(2) V(-1) s(-1) was observed for based transistors under ambient conditions, suggesting quinoidal benzo[1,2-b:4,5-b']dithiophene is an excellent acceptor unit in D-A type n-channel organic semiconductors.

Weak epitaxy growth of phthalocyanine on inducing layers of fluorinated 5,5"-bis(biphenyl-4-yl)-2,2':5',2"-terthiophene.

Weak epitaxy growth (WEG) is an effective method in the preparation of high-mobility thin films of disk-like organic semiconductors. The growth behavior and quality of the epitaxial thin film are closely related to the inducing layers. Here, a series of fluorinated molecules, 5,5"-bis(3'-fluoro-biphenyl-4-yl)-2,2':5',2"-terthiophene (m-F2BP3T), 5,5"-bis(3',5'-difluoro-biphenyl-4-yl)-2,2':5',2"-terthiophene (F4BP3T), and 5,5"-bis(4'-fluoro-biphenyl-4-yl)-2,2':5',2"-terthiophene (p-F2BP3T) as well as a referenced molecule 5,5"-bis(biphenyl-4-yl)-2,2':5',2"-terthiophene (BP3T), are introduced to serve as inducing layers for the epitaxy growth of phthalocyanine. Compared to the nonfluorinated inducing layer, the interactions between the fluorinated inducing layer and phthalocyanine might be relatively strong due to the potential existence of C-H···F weak hydrogen bonds. The growth behavior and mechanism of phthalocyanine on the fluorinated inducing layers are investigated by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXD), selected area electron diffraction (SAED). According to the AFM and SAED, H(2)Pc presents a selective epitaxy growth depending on the position of fluorine: epitaxy growth on m-F2BP3T and F4BP4T, and nonepitaxy growth on p-F2BP3T. Comparison of CuPc with F(16)CuPc on monolayer p-F2BP3T further revealed that the uncommon nonepitaxy growth behavior of H(2)Pc (CuPc) on p-F2BP3T mainly originates from the enhanced interactions between the two types of molecules. As a consequence, the capability of molecules orienting themselves along the surface channel is decreased; meanwhile, the demand of the upper limit of the lattice mismatch is more rigorous for commensurate epitaxy. Finally, the oriented nucleation of H(2)Pc (CuPc) on monolayer p-F2BP3T is affected, and netlike crystals are formed. The sudden change of H(2)Pc (CuPc) from multiorientation on monolayer to just one orientation on double-layer p-F2BP3T suggests that there is a critical lattice mismatch value for commensurate epitaxy in WEG when the molecule-substrate interactions are enhanced.