Rare solvent annealing effective benzo(1,2-b:4,5-b')dithiophene-based low band-gap polymer for bulk heterojunction organic photovoltaics

A newly synthesized benzo(1,2-b:4,5-b')dithiophene-based low band-gap copolymer pBCN is amenable to solvent annealing in the fabrication of organic photovoltaics, of which power conversion efficiency is greatly improved to 4.2% with PC(61)BM or 4.9% with PC(71)BM.     

A novel dialkylthio benzo[1,2-b:4,5-b']dithiophene derivative for high open-circuit voltage in polymer solar cells

A new dialkylthio benzo[1,2-b:4,5-b']dithiophene (S-BDT) was designed and synthesized and the polymer S-PBDT was prepared by a Stille coupling reaction. A high open-circuit voltage (V(oc)) of up to 0.99 V was achieved in polymer solar cells with PCBM.     

Organic dyes incorporating the benzo[1,2-b:4,5-b']dithiophene moiety for efficient dye-sensitized solar cells

A new class of organic sensitizers incorporating a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as conjugated spacer has been synthesized and successfully used for dye-sensitized solar cells (DSSCs). The length of the π-conjugated spacers has a strong impact on electro-optical properties of these dyes, leading to the conversion efficiencies ranging from 4.17 to 5.68% under AM 1.5 G irradiation. This result indicates that the BDT unit is a promising candidate in organic sensitizers.     

Investigations of substituted benzofuran-3-carboxylates,benzo[1,2-b:4,5-b']difurans and benzo[1,2-b:4,3-b']difurans

The Michael addition of ethyl acetoacetate to benzoquinone, toluquinone, and chlorobenzo-quinone leads to formation of substituted 5-hydroxybenzofuran-3-earboxylates and linear benzo-[1,2-b:4,5-b']difurans. The previously reported structural proof for the benzodifurans obtained from chlorobenzoquinone and toluquinone, although correct in the conclusion, is shown to be invalid. Proof of the linear benzodifuran structures was obtained by comparison of the uv spectra with authentic angular benzo[1,2-b:4,3-b']difurans.     

Synthesis, properties, and structures of benzo[1,2-b:4,5-b']bis[b]benzothiophene and benzo[1,2-b:4,5-b']bis[b]benzoselenophene

Employing two consecutive cyclization reactions, benzo[1,2-b:4,5-b']bis[b]benzochalcogenophenes, which are pi-extended heteroarenes, were efficiently synthesized. Their electronic and crystal structures were elucidated on the basis of UV-vis spectra, electrochemical measurements, and X-ray structural analyses.     

A Near-infrared Non-fullerene Acceptor with Thienopyrrole-expanded Benzo[1,2-b:4,5-b′]dithiophene Core for Polymer Solar Cells

A near-infrared non-fullerene acceptor(NFA) BDTIC, based on thienopyrrole-expanded benzo[1,2-b:4,5-b′]dithiophene unit(heptacyclic S,N-heteroacene) as core, is designed and synthesized. The aromatic pyrrole ring with strong electron-donating ability in the core enhances the intramolecular charge transfer effect, finely tunes the optical bandgap and absorption profile of BDTIC, and thus results in a narrowed optical bandgap(E_g~(opt)) of 1.38 eV and a near-infrared absorption to 900 nm. When BDTIC is paired with donor polymer PBDB-T to fabricate organic solar cells, the optimized device achieves a best power conversion efficiency of 12.1% with a short-circuit current density of 20.0 mA·cm~(-2) and an open-circuit voltage of 0.88 V. The photovoltaic performance benefits from the broad absorption, weak bimolecular recombination, efficient charge separation and collection, and favorable blend morphology. This work demonstrates that thienopyrroleexpanded benzo[1,2-b:4,5-b′]dithiophene unit(heptacyclic S,N-heteroacene) is a promising building unit to construct high-performance NFAs by enhancing the intramolecular charge transfer effect, broadening absorption as well as maintaining good intermolecular stacking property.     

6,12-二(三乙基硅乙炔基)二苯并苯并二噻吩的合成、表征及性能研究

合成了6,12-二(三乙基硅乙炔基)二苯并[d,d’]苯并[1,2-b;4,5-b’]二噻吩,并通过熔点测定、元素分析、核磁共振谱、质谱及X-单晶衍射分析对其进行了表征,同时对其作为有机场效应管(OFET)材料的性能进行了测试.结果表明,该材料在器件中载流子迁移率高达0.53 cm2/Vs,开关比为105.     

Development of naphtho[1,2-b:5,6-b']dithiophene based novel small molecules for efficient bulk-heterojunction organic solar cells

Two new small molecules with a rigid planar naphtho[1,2-b:5,6-b']dithiophene (NDT) unit were designed and synthesized. Solution processed bulk-hetereojunction organic solar cells based on blends of the small molecules and [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) exhibited promising photovoltaic device performance with a maximum power conversion efficiency up to 2.20% under the illumination of AM 1.5G, 100 mW cm(-2).     

Facile synthesis, structure, and properties of benzo[1,2-b:4,5-b']dichalcogenophenes

[reaction, structures: see text] A general and convenient synthesis of benzo[1,2-b:4,5-b']dichalcogenophenes including the thiophene (BDT, 1), selenophene (BDS, 2), and tellurophene (BDTe, 3) homologues is developed. Thus synthesized heterocycles are structurally characterized by single-crystal X-ray analysis, and all three homologues are isostructural with one another. They all have completely planar molecular structures packed in a herringbone arrangement. Their physicochemical properties were also elucidated by means of cyclic voltammetry (CV) and UV-vis spectra.     

Enhanced photocatalytic hydrogen production under visible light of an organic-inorganic hybrid material based on enzo[1,2-b:4,5-b']dithiophene polymer and TiO2

Titanium dioxide (TiO₂) has been limited in photocatalysis due to its wide band gap (3.2 eV) and limited absorption in the ultraviolet range. Therefore, organic components have been introduced to hybrid with TiO₂ for enhanced photocatalytic efficiency under visible light. Here, we report that benzo[1,2-b:4,5-b']dithiophene polymer was an ideal organic material for the preparation of a hybrid material with TiO₂. The energy band gap of the resulting hybrid material decreased to 2.9 eV and the photocatalytic hydrogen production performance reached 745.0 µmol g^?1 h^?1 under visible light irradiation. Meanwhile, the material still maintained the stability of hydrogen production performance after 40 h of photocatalytic cycles. The analysis of the transient current response and electrochemical impedance revealed that the main reasons for the enhanced water splitting of the hybrid materials were the faster separation of electron hole pairs and the lower recombination of photocarrier ions. Our findings suggest that polythiophene is a promising organic material for exploring hybrid materials with enhanced photocatalytic hydrogen production.     

Synthesis and properties of a series of well-defined and polydisperse benzo[1,2-b:4,3-b']dithiophene oligomers

Monodisperse and polydisperse oligomers of benzo[1,2-b:4,3-b']dithiophene (BDT) (1-14), including three types of oligomers with different spacers combining BDT units (direct linkage, vinylene spacers, and ethynylene spacers), were synthesized, and their thermal, optical, and electrochemical properties were investigated. The oligomers were synthesized using Suzuki, Stille, Wittig, and Sonogashira coupling reactions. All of the monodisperse oligomers showed high melting points and 5% weight loss temperatures (T(d) > 400 degrees C). The fluorescence maxima of all oligomers were red-shifted, and the emission colors varied from blue to yellow as the chain lengths-and thus the conjugation lengths-increased. The vinylene-bridged oligomers emitted at longer wavelengths than the direct-linked and ethynylene-bridged oligomers. UV-vis absorption spectra in toluene solution indicated an effective conjugation length of about six BDT units for polydisperse oligomer 5. Cyclic voltammetry measurement indicated that tetramer 3 had high electrochemical stability. Although tetramer 3 and vinylene-bridged tetramer 8 exhibited reversible oxidation waves, ethynylene-bridged tetramer 13 showed an irreversible oxidation process. Each type of monodisperse oligomer exhibited higher HOMO levels with increasing chain length.     

The preparation of the benzo[4,5]cyclohepta[1,2-b]pyrazine and benzo[4,5]cyclohepta[1,2-b]quinoxaline systems

Benzo[4,5]cyclohepta[1,2-b]quinoxaIine 2 , benzo[4,5]cyclohepta[1,2-b]pyrazine 3a and benzo[4,5]cyclohepta[1,2-b]quinoxaline 4 were prepared from 4,5-benzotropolone and 1,2-phenylenediamine, ethylenediamine and 1,2-diaminocyclohexane, respectively. Compound 3a was methylated to 3b .     

Benzo[1,2-b:4,5-b']bis[b]benzothiophene as solution processible organic semiconductor for field-effect transistors

Coplanar benzo[1,2-b:4,5-b']bis[b]benzothiophenes (, ) for the application in organic field-effect transistors were synthesized by a simple two-step procedure involving triflic acid induced ring-closure reaction; such solution processed devices show a hole mobility of up to 0.01 cm(2) V(-1) s(-1).     

基于苯并二噻吩的D-A型窄带隙共轭聚合物在太阳能电池中的应用

近年来为获得有机聚合物太阳能电池更高的能量转换效率,越来越多的活性层材料被设计合成出来,尤其是给体材料。其中,基于给体单元苯并二噻吩(BDT)的D-A型窄带隙共轭聚合物更是多次刷新了有机聚合物太阳能电池效率的最高记录,目前达10.6%。本文探讨了基于苯并二噻吩的D-A型窄带隙共轭聚合物材料结构及其应用在太阳能电池中的性能参数关系,从提高开路电压、短路电流和填充因子三个方面总结出了提高基于BDT共轭聚合物太阳能电池能量转换效率的方法。     

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes: a new class of high-performance semiconductors for organic field-effect transistors

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b']diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1.     

Synthesis and characterization of benzo[1,2-b:3,4-b':5,6-b']trithiophene (BTT) oligomers

Two dimers (2 and 3), dendritic tetramer (4), hexamer (5), and decamer (6) of benzo[1,2-b:3,4-b':5,6-b']trithiophene (BTT), a potential π-core unit with C(3h) symmetry, were synthesized, characterized, and evaluated for possible use as organic semiconductors. Single crystal X-ray analyses of the dimers (2 and 3) revealed that they have planar molecular structures with dihedral angles of almost 180° between two BTT units. In accordance with the rigid and planar molecular structure, the unsubstituted dimer (2) is poorly soluble, whereas the octyl-substituted dimer (3) has improved solubility. Although the solubility of the dendritic tetramer (4) is decreased, further extended systems, i.e., the dendritic hexamer (5) and decamer (6), have solubilities better than that of 4. With increasing numbers of BTT units in the molecule, the experimentally determined energy levels of HOMO shift upward slightly and the HOMO-LUMO energy gaps become smaller, but the extent of HOMO destabilization and reduction of the HOMO-LUMO gap are not significant. Taking into account the energy levels of the frontier orbitals, 3-6 could be useful as p-channel organic semiconductors rather than n-channel. In fact, the spin-coated thin film of 3 with edge-on molecular orientation acted as an active channel of field-effect transistors that showed hole mobilities as high as 0.14 cm(2) V(-1) s(-1), indicating that the BTT core is a useful π-conjugated system for application to organic semiconductors, although 4-6 gave FET characteristics rather inferior to those of 3, owing to their amorphous nature in the thin film state.     

Synthesis of a 4,8-dialkoxy-benzo[1,2-b:4,5-b']difuran unit and its application in photovoltaic polymer

A new building block of benzo[1,2-b:4,5-b']difuran (BDF) was firstly designed and synthesized. The newly designed unit was applied for constructing a new photovoltaic low band gap polymer, PBDFDTBT, which exhibited promising power conversion efficiency of 5.0%.     

2,3,9,10-Tetrachlorobenzo[1,2-b: 4,5-b']bis[1,4]benzodioxin,a homologue of TCDD

Catechol and 4,5-dichlorocatechol have been condensed with 1,5-dichloro-2,4-dinitrobenzene to provide benzo[1,2-b: 4,5-b ]bis[1,4]benzodioxin and its 2,3,9,10-tetrachloro derivative, respectively. The latter compound is a novel homologue of the extremely toxic 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD).     

A new route to benzo[4,5]cyclohepta[1,2-b]naphthalenes: synthesis of radermachol

[formula: see text] Condensation of 3-phenylsulfonyl-1,3-isobenzofuranone (3) with benzocyclohept-6,7-en-5-ones such as 4 and 15 provides a straightforward, general method for synthesis of functionalized benzo[4,5]cyclohepta[1,2-b]naphthalenes (e.g., 5 and 16). This finding was used to achieve a brief and efficient preparation of 6,7-benzo-3,4-(1,4-dimethoxy-2,3-naphtho)-1,5-dioxosuberane (2), an established intermediate to the naturally occurring red pigment radermachol (1).