Ladder-type Diindenopyrazine Based Conjugated Copolymers for Organic Solar Cells with High Open-circuit Voltages

A ladder-type diindenopyrazine （IPY） was synthesized and used as a building block for constructing conjugated copolymers. Three copolymers based on the IPY moiety were obtained via the Suzuki coupling reaction with dif- ferent monomers, including 4,7-dithien-2-yl-2,1,3-benzothiadiazole （DBT）, 5,8-dithien-2-yl-2,3-diphenylquinoxa- line （DTQ）, and 5,8-dithien-2-yl-2,3-di（4-fluorophenyl）quinoxaline （DFTQ）. The obtained polymers were charac- terized by 1H NMR spectroscopy, UV-Vis absorption spectroscopy, cyclic voltammetry, and gel permeation chro- matography （GPC）. Owing to the four solubilizing alkyl chains on the IPY unit, all the three copolymers have good solubility in common solvents. These polymers have deep-lying HOMO energy levels in the range of-5.55-5.60 eV, and exhibit field-effect mobilities as high as 0.006 cm2.V-l.s i. Photovoltaic applications of these polymers as light-harvesting and hole-conducting materials were investigated in conjunction with [6,6]-phenyl-C6rbutyric acid methyl ester （PC61BM）. Both conventional and inverted devices were fabricated based on these three polymers. A power conversion efficiency （PCE） of 2.53% and a high open-circuit voltage of 1.00 V were obtained under simu- lated solar light AM 1.5 G （100 mW/cm2） from an inverted solar cell with an active layer containing 25 wt% lad- der-type IPY containing copolymer （PIPYDTQ） and 75 wt% PC61BM. Moreover, a high open-circuit voltage of 1.02 V and a PCE of 2.40% were achieved from a conventional solar cell based on PIPYDTQ.     

Efficient Polymer Solar Cells Based on Solution-processed Vanadium Oxide as Hole-extracting Layer

Here we reported the fabrication of efficient polymer solar cells from regioregular poly（3-hexylthiophene） （P3HT）：fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester （PC6jBM） mixtures, in which solution- processed vanadium oxide （VOx） was used as a hole-extracting layer （HEL）. The obtained devices exhibited a high power conversion efficiency of 3.96%, and can be enhanced to 4.06% and 4.16%, respectively, when two types of PEDOT：PSS with different conductivities were used in conjunction with the VOx layer. All the VOx-based devices showed a high fill factor （FF） over 70%, which was ascribed to efficient hole extracting efficiency associated with the solution-processed VOx hole-extracting layer. The origins of the improvement were also studied by transmission spectra, atomic force microscope （AFM）, and capacitance-voltage characteristics.     

An isoindigo-based low band gap polymer for efficient polymer solar cells with high photo-voltage

A new low band gap polymer (E(g) = 1.6 eV) with alternating thiophene and isoindigo units was synthesized and characterized. A PCE of 3.0% and high open-circuit voltage of 0.89 V were realized in polymer solar cells, which demonstrated the promise of isoindigo as an electron deficient unit in the design of donor-acceptor conjugated polymers for polymer solar cells.     

Improved Photovoltaic Performance of MEH-PPV/PCBM Solar Cells via Incorporation of Si Nanocrystals

We have studied the effect of silicon nanocrystals （SiNCs） as a third component on performance of organic bulk heterojunction solar cells composed of poly[2-methoxy,5-（2＇-ethylhexyloxy）-l,4-phenylene vinylene] （MEH- PPV）：[6,6]-phenyI-C61-butyric acid methyl ester （PCBM） blend film. By adding suitable amounts of SiNCs into MEH-PPV：PCBM blend, the device performance such as external quantum efficiency, short circuit current density （Js（）, and power conversion efficiency （PCE） improved. Incorporation of 2.5% SiNCs in the blend led to 13.6% improvement of Jsc, which in turn resulted in 18% improvement of PCE up to 2.28%. The improved performance was mainly due to the improvements both in the charge generation from the interface of MEH-PPV/SiNCs and the charge collection at the cathode.     

Donor-Acceptor Oligomers and Polymers Composed of Benzothiadiazole and 3-Hexylthiophene： Effect of Chain Length and Regioregularity

A series of donor-acceptor oligomer OBTThn （n = 1- 7） and polymer PBTThl and PBTTh2 composed of al- ternative 2,1,3-benzothiadiazole and 3-hexylthiophene have been designed and synthesized for the purpose of in- vestigation on the effect of chain length and side-chain regioregularity on their basic properties and photovoltaic performance. In the OBTThn oligomers and PBTThl polymer, all the hexyl side chains on thienyl units orient to- ward the same direction. Upon elongation of the chain length, the intramolecular charge transfer （ICT） absorption band in solution gradually redshifts from 398 nm for OBTThl to 505 nm for OBTThT, then to 512 nm for PBTThl polymer. Meanwhile, the HOMO energy level increases from -5.45 eV （OBTTh0 to -5.08 eV （OBTThT） and -5.09 eV （PBTThl）, and the LUMO energy level decreases from -3.11 eV （OBTTh0 to -3.30 eV （OBTThT） and -3.33 eV （PBTThl）, thus giving a smaller and smaller energy bandgap for higher oligomers and polymers. Theo- retical calculation suggests straight line-like backbone geometry for this series of oligomers and polymer. On the other hand, polymer PBTTh2 possesses a different side-chain regioregularity, in which every two neighbor hexyl side chains are arranged in different orienting direction. It is theoretically suggested to have curved line-like back- bone geometry. In solution, it shows similar photophysical and electrochemical properties as PBTThl. However in film state, it displays a less redshift in the ICT band as refer to that in solution than PBTThl. In combination with [6,6]-phenyl-C61-butyric acid methyl ester （PC61BM）, these oligomers and polymers were used as donor material to fabricate organic bulk heterojunction solar cells. Again, chain length-dependent device photovoltaic performance was observed. The device based on OBTTh4 showed a power conversion efficiency of 0.16%, while it increased to 0.36% and 0.49% for the devices based on OBTTh6 and PBTThb respectively. However, the side-chain regio- regularity has less influence on the device photovoltaic output since the device based on PBTTh~ displayed an effi- ciency of 0.52%, comparable to that of PBTThl.     

Dithieno[a,e]pentalene Based Conjugated Polymers： Synthesis and Characterization

The concept of introducing n-conjugated but anti-aromatic repeating units into conjugated polymers has been explored. The thermal stability, optical and electrochemical properties of dithieno[a,e]pentalenes （DTP） based polymers have been studied. The effect of introducing electron withdrawing repeating units into DTP based poly- mer on the physical properties of polymer has also been investigated. The new polymers showed broad absorption in visible and near-infrared region.     

Controlled conjugated backbone twisting for an increased open-circuit voltage while having a high short-circuit current in poly(hexylthiophene) derivatives

Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone--due to an increase in the polymer ionization potential--while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2':5',2'-terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current.     

Synthesis and Structure of {（Tab-Tab）[Ag2（μ-Cl）41.2MeCN}n （Tab = 4-（Trimethylammonio）benzenethiolate）

In the presence of Et4NCl·H2O, reaction of AgCl with TabHPF6 in MeCN afforded the title complex {（Tab-Tab）[Ag2（μ-Cl）4]-2MeCN}n 1. 1 crystallizes in the orthorhombic space group Pbcn with a = 16.782（3）, b = 6.8358（14）, c = 26.194（5） A, V = 3004.9（10） A3, Z = 8,μ = 1.817 mm^-1, Dc = 1.711 g/cm3, T= 223 K, C1lH16AgCl2N2S, Mr= 387.10, F（000） = 1544, S= 1.160, R = 0.0528 and wR = 0.0896 for 2732 observed reflections with I 〉 2σ（I）. 1 contains a 1D linear [Ag2Cl4]n^2n- chain coupled with the [Tab-Tab]2＋ dications. Intermolecular hydrogen bonding interactions between the protons of methyl groups from the Tab-Tab dications and the chlorides result in the formation of a 2D hydrogen-bonded network.     

Catena-dichloro（4,4＇-dimethyl-2,2＇-bipyridine） Cadmium（Ⅱ）, a New One-dimensional Chain with Blue Fluorescent Emission

A new μ-chloro-bridged one-dimensional coordination polymer [Cd（dmbpy）Cl2]a （dmbpy = 4,4＇-dimethyl-2,2＇-bipyridine） has been synthesized and structurally characterized by elemental analyses, IR, UV spectra and single-crystal X-ray diffraction. The complex crystallizes in the monoclinic system, space group C2/c with a = 17.745（4）, b = 10.326（2）, c = 7.3382（15）A, β = 106.85（3）°, V = 1286.9（4）A^3, Z = 4, C12H12N2Cl2Cd, Mr = 367.54, Dc = 1.897 g/cm^3, F（000） = 720, 2（MoKα） = 0.71073 A,μ= 2.089 mm^-1, R = 0.0368 and wR = 0.1048 for 1041 observed reflections （I 〉 2σ（I））. Cadmium（Ⅱ） adopts a distorted octahedral coordination geometry and adjacent coordination chains are intercalated in a zipper-like fashion into 2D layers through the π-π stacking interactions between dmbpy. Fluorescent analyses show that it exhibits intense blue photoluminescence in both DMF and DMSO solutions at room temperature.     

Hydrothermal Synthesis and Crystal Structure of a Zinc（Ⅱ） Polymer with a Two-dimensional Layer Structure： [Zn（pzdc）（phen）]n·nH2O

A metal-organic coordination compound formulated as [Zn（pzdc）（phen）]n·nH2O 1 （H2pzdc = pyrazine-2,3-dicarboxylic acid, phen = 1,10-phenanthroline） has been hydrothermally synthesized and structurally characterized by elemental analysis, IR, fluorescence spectrum and single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic system, space group P21/n with a = 11.607（2）, b = 11.719（2）, c = 13.140（3）A^°, β = 110.707（3）°, V= 1671.9（6）A^°3, C18H12ZnN4O5, Mr= 429.69, De = 1.707 g/cm^3,μ（MoKa） = 1.511 mm^-1, F（000） = 872, Z = 4, the final R = 0.0356 and wR = 0.0853 for 2713 observed reflections （I 〉 2σ（I））. It exhibits an interesting two-dimensional layer structure and shows yellow photoluminescent property at room temperature.     

Construction of a 3D Co（II） Framework Based on Two Type of V-shaped Bidentate Ligands

A three-dimensional （3D） coordination polymer {[Co（bdc）（dpb）]·H2O}n （1） was prepared by solvothermal reaction of 1,3-dipyridyl benzene （dpb） with deprotonated 1,3-benzene- dicarboxylate （H2bdc）, and was characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. It crystallizes in the monoclinic system, space group C2/c with α = 15.478（6）, b = 12.865（5）, c = 24.091（10） ？, β = 95.599（5）°, V = 4774（3） ？3, C24H18CoN2O5, Mr = 473.34, Dc = 1.267 g/cm3, F（000） = 1864.0, μ = 0.748 mm-1 and Z = 8. Each Co（II） ion links three bdc2- anions to form an infinitely 1D ladder-shaped chain containing binuclear [（COO）Co]2 cluster, and dpb links adjacent 1D chains to form a 3D pcu framework. In addition, the UV-vis of 1 was also studied.     

Recent Advances of Lanthanide-transition Heterometallic Coordination Polymers

With the improvement of high-tech and emergence of crossing and new fields,lanthanide-transition(Ln–M) heterometallic coordination polymers have attracted much attention of many researchers,which exhibit novel structures and unique properties with potential applications in the nonlinear optical materials,fluorescent materials,superconducting materials,magnetic materials,catalysis,bio-simulation,adsorption and separation,and so on.It is thus necessary to summarize Ln–M heterometallic coordination polymers.According to the transition metal ions,those coordination polymers are divided into six parts to explore the current applications and future developments.     

Synthesis and Crystal Structure of a 1D Alternate Chain Polymer [Zn2（NBA）2（4,4′-bipy）]n

A one-dimensional zinc-containing coordination polymer, [Zn2（NBA）2（4,4′-bipy）]n （NBA = 3-nitrobenzoic acid, 4,4′-bipy = 4,4′-bipyrindine）, has been solvothermally synthesized and characterized by single-crystal X-ray diffraction, IR and elemental analysis. The crystal structure is of monoclinic, space group C2/c with a = 24.6478（2）, b = 14.0964（3）, c = 11.4275（2）A, β=108.7870（10）°, V = 3758.89（11） ,A^3, C38H20N6O16Zn2, Mr = 947.34, Z = 4, De = 1.674 g/cm^3 μ= 1.363 mml, F（000） = 1912, R = 0.0720 and wR = 0.2277 for 2841 observed reflections （I 〉 2σ（I）. In this compound, NBA in syn-syn coordination mode bridges zinc centers into dimericzinctetracarboxylate [Zn2（COO）4] secondary building units （SBUs） which are linked through μ-4,4′-bpy affording 1D alternating chains. These adjacent chains are further stacked through intermolecular π...π interactions to form a 3D framework.     

Synthesis and Structure of a Two-dimensional Double Chain Iron（Ⅱ） L-Trp Coordination Polymer [Fe（L-trp）e（HL-trp）2]n

The title complex [Fe（L-trp）2（HL-trp）2]n （L-trp = L-tryptohan or 2-amino-3-（1H -indol-3-yl）-propanoic acid） has been formed by a hydrothermal method involving hexaaquacobaltous perchlorate and L-tryptophan. The product was characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P211c, with a = 19.828（3）, b = 5.4233（14）, c = 9.2796（16） A, β= 97.691（2）°, V = 988.9（3） A3, Z = 2, Mr = 462.29, Dx = 1.553 g/cm3, F（000） = 480,/a = 0.802 mm^-1, the final R = 0.0399 and wR = 0.0930 for 1738 observed reflections with I 〉 2σ（/）. The structural analysis shows that the complex assumes a two-dimensional double chain plane structure.     

One-dimensional Coordination Polymers of rctt-1,3-Diphenyl-2,4-bis [2-（5-phenyl）- oxazolyl]cyclobutane with CuCI2 and COCl2

The Cu（Ⅱ） and Co（Ⅱ） supramolecular coordination polymers, [CuCl2（DPO）- （CH3CN）0.5（CH2Cl2）0.5]n （CuDPO, DPO = rctt-1,3-diphenyl-2,4-bis[2-（5-phenyl）oxazolyl]cyclo- butane） and [CoCl2（DPO）]n （CoDPO）, were synthesized and characterized by single-crystal X-ray diffraction method. CuDPO crystallizes in monoclinic, space group P21/n, with a = 11.243（5）, b = 16.070（8）, c = 19.872（9） A, β = 95.678（10）°, Z = 4, V= 3573（3） A3, C35.50H28.50Cl3CuN2.50O2, Mr = 692.00, Dc = 1.287 g/cm3, p = 0.868 mm^-1, F（000） = 1420, S = 1.089, （△/σ）max = 0.069, the final R = 0.0682 and wR = 0.1749. CoDPO is of monoclinie, space group P21/n, with a = 11.396（4）, b = 15.151（5）, c = 17.673（6） A, β = 90.528（6）°, Z = 4, V = 3051.4（17） A3, C34H26Cl2CoN2O2, Mr = 624.40, Dc = 1.359 g/cm3, μ = 0.770 mm^-1, F（000） = 1284, S = 0.981, （△/σ）max = 0.001, the final R = 0.0471 and wR = 0.0961. In each case, the metal cation is coordinated by two C1 anions and two N atoms from oxazole ring of the ligands, which leads to the formation of a one-dimensional polymeric structure. It is found that the cyclobutane ring of coordinated DPO adopts a distorted conformation in the crystal, which is attributed to the increased steric effect between adjacent aryl substituents for the coordination of oxazole ring to metal cation. Thermal gravimetric analysis of the two complexes was also observed.     

Synthesis and Crystal Structure of a Novel Ca(Ⅱ) Coordination Polymer Containing Dipyridine Dicarboxylic Ligand

The novel alkaline metal complex Ca(BPDCH)2(1, BPDCH2 = 2,2'-bipyridine-5,5'-dicarboxylic acid) has been synthesized by the hydrothermal reaction of Ca(NO3)2·4H2O with 2,2'-bipyridine-5,5'-dicarboxylic acid. The molecular and crystal structures of complex 1 have firstly been characterized by FTIR, elemental analysis, and X-ray single-crystal diffraction. The 3D MOF structure of complex 1 was interpreted by the versatile binding modes-the intermolecular hydrogen bonds and π-π stacking interactions of 2,2'-bipyridine-5,5'-dicarboxylic acid ligand. The analysis results show complex 1 belongs to a coordination polymer with 3D MOF structure. The results of thermogravimetric analysis and solubility demonstrate complex 1 is a thermostable compound and does not dissolve in water and traditional organic solvents.     

Hydrothermal Synthesis and Crystal Structure of a New Three-dimensional Co（II） Coordination Polymer Based on 2,3-Thiophenedicarboxylic Acid

A new Co（ll） polymer [Co（tdc）（l,4-bimb）]n 1 （H2tdc = thiophene-2,3-dicarboxy- lic acid, 1,4-bimb -- 1,4-bis（imidazol-1 ＇-yl）butane） was synthesized under hydrothermal conditions The compound crystallizes in the monoclinic system, space group C2/c with a = 15.643（9）, b = 8.839（5）, c=12.952（7） A, β = 105.964（6）°, V= 1721.8（16） A3, Z = 4, Mr = 419.32, Dc= 1.618 Mg/m3,μ = 1.149 mm-1, F（000） = 860, the final R = 0.0243 and wR =0.0613 for 1460 observed reflections with I 〉 2σ（I）. The compound presents a three-dimensional （3D） network extended by both tdc2- anions and 1,4-bimb ligands in which the tdc2- anions employ a chelating coordination mode. From the topology point of view, the structure could be described as a 3D 4-connected 65.8 CdSO4-type net. Infrared spectroscopy, elemental analyses, thermogravimetric analysis and powder X-ray diffraction properties of 1 are also investigated.     

Synthesis,Crystal Structure and Photoluminescence of a New Zn(Ⅱ) Dimer Constructed by 1,10-Phenanthroline Derivative and Flexible Dicarboxylate

A new compound,[Zn(L)(1,4-chdc)]2·2H2O(1,1,4-chdc = 1,4-cyclohexanedicarboxylate and L = 11-fluoro-dipyrido[3,2-a:2,3-c]phenazine),has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction.The crystal of 1 belongs to triclinic,space group P1 with a = 9.4679(19),b = 10.915(2),c = 12.577(3) ,α = 77.22(3),β = 74.73(3),γ = 65.47(3)°,C52H39F2N8O10Zn2,Mr = 1104.65,V = 1131.4(4) 3,Z = 1,Dc = 1.621 g/cm3,S = 1.091,μ(MoKα) = 1.143 mm–1,F(000) = 565,R = 0.0426 and wR = 0.1171.In 1,two 1,4-chdc anions bridge two Zn(Ⅱ) atoms to form a dimer.The neighboring dimers are further extended by π-π stacking interactions to form a 2D supramolecular layer.The luminescent property of the compound has also been investigated.     

Synthesis and Characterization of a New 2D Ca(Ⅱ) Coordination Polymer Containing 1D Calcium-oxygen Chains

A new 2D Ca(Ⅱ) coordination polymer, [Ca(H2btc)(H2O)2]n(1, H4 btc = biphenyl-3,3',5,5'-tetracarboxylic acid), has been synthesized using the hydrothermal method and characterized by single-crystal X-ray diffraction, elemental analysis, IR, thermogravimetric analysis, and photoluminescent analysis. Complex 1 crystallizes in the monoclinic system, space group C2/c with a = 17.5676(15), b = 11.4496(8), c = 7.6197(8)A, β = 102.787(2)o, V = 1494.6(2) A3, Z = 4, D3 c = 1.797 Mg·m-, μ = 0.483 mm-1, F(000) = 832, the final R = 0.0348 and wR = 0.0915 for 1521 observed reflections with I 2σ(I). Complex 1 has a 2D network containing 1D calcium-oxygen chains. These 2D networks are further connected by O–H···O hydrogen bonding interactions to generate a 3D supramolecular structure.     

Synthesis and Crystal Structure of a Palladium（H） Coordination Polymer [Na2Pd（2,6-pydc）2（H2O）6]n

A novel coordination polymer [Na2Pd（2,6-pydc）2（H2O）6]n （2,6-H2pydc = 2,6-pyridinedicarboxylic acid） has been synthesized and its crystal structure was determined by single-crystal X-ray diffraction. The crystal belongs to the monoclirtic system, space group P21/c, with a = 11.962（2）, b = 6.5552（13）, c = 12.673（3） A, β = 91.72（3）^o, V = 993.3（3） A^3, Z = 2, Mr = 590.68, Dc = 1.975 g/cm^3,μ = 1.059 mm^-1, F（000） = 592, the final R = 0.0211 and wR = 0.0454. In the crystal the Pd（II） ion adopts a distorted four-coordinated square-planar geometry and bonds to two bidentate 2,6-pyridinedicarboxylate molecules through caronyl oxygen and pyridine nitrogen atoms. The title complex exhibits a novel three-dimensional network structure.