Self‐Doped,n‐Type Perylene Diimide Derivatives as Electron Transporting Layers for High‐Efficiency Polymer Solar Cells

Perylene diimide (PDI) with high electron affinities are promising candidates for applications in polymer solar cells (PSCs). In addition, the strength of π‐deficient backbones and end‐groups in an n‐type self‐dopable system strongly affects the formed end‐group‐induced electronic interactions. Herein, a series of amine/ammonium functionalized PDIs with excellent alcohol solubility are synthesized and employed as electron transporting layers (ETLs) in PSCs. The electron transfer properties of the resulting PDIs are dramatically tuned by different end‐groups and π‐deficient backbones. Notably, electron transfer is observed directly in solution in self‐doped PDIs for the first time. A significantly enhanced power conversion efficiency of 10.06% is achieved, when applying the PDIs as ETLs in PTB7‐Th:PC₇₁BM‐based PSCs. These results demonstrate the potential of n‐type organic semiconductors with stable n‐type doping capability and facile solution processibility for future applications of energy transition devices.     

Thiophene Rings Improve the Device Performance of Conjugated Polymers in Polymer Solar Cells with Thick Active Layers

Developing novel materials that tolerate thickness variations of the active layer is critical to further enhance the efficiency of polymer solar cells and enable large‐scale manufacturing. Presently, only a few polymers afford high efficiencies at active layer thickness exceeding 200 nm and molecular design guidelines for developing successful materials are lacking. It is thus highly desirable to identify structural factors that determine the performance of semiconducting conjugated polymers in thick‐film polymer solar cells. Here, it is demonstrated that thiophene rings, introduced in the backbone of alternating donor–acceptor type conjugated polymers, enhance the fill factor and overall efficiency for thick (>200 nm) solar cells. For a series of fluorinated semiconducting polymers derived from electron‐rich benzo[1,2‐b:4,5‐b′]dithiophene units and electron‐deficient 5,6‐difluorobenzo[2,1,3]thiazole units a steady increase of the fill factor and power conversion efficiency is found when introducing thiophene rings between the donor and acceptor units. The increased performance is a synergistic result of an enhanced hole mobility and a suppressed bimolecular charge recombination, which is attributed to more favorable polymer chain packing and finer phase separation.     

Placental 5-methylcytosine and 5-hydroxymethylcytosine patterns associate with size at birth

Altered placental function as a consequence of aberrant imprinted gene expression may be one mechanism mediating the association between low birth weight and increased cardiometabolic disease risk. Imprinted gene expression is regulated by epigenetic mechanisms, particularly DNA methylation (5mC) at differentially methylated regions (DMRs). While 5-hydroxymethylcytosine (5hmC) is also present at DMRs, many techniques do not distinguish between 5mC and 5hmC. Using human placental samples, we show that the expression of the imprinted gene CDKN1C associates with birth weight. Using specific techniques to map 5mC and 5hmC at DMRs controlling the expression of CDKN1C and the imprinted gene IGF2, we show that 5mC enrichment at KvDMR and DMR0, and 5hmC enrichment within the H19 gene body, associate positively with birth weight. Importantly, the presence of 5hmC at imprinted DMRs may complicate the interpretation of DNA methylation studies in placenta; future studies should consider using techniques that distinguish between, and permit quantification of, both modifications.     

An Ultra‐Mechanosensitive Visco‐Poroelastic Polymer Ion Pump for Continuous Self‐Powering Kinematic Triboelectric Nanogenerators

A mechanosensitive, visco‐poroelastic polymer ion pump that can rapidly establish a dense electrical double layer via mechanical pressure, thereby significantly enhancing output performance of an ionic triboelectric nanogenerator (iTENG), is described. A working mechanism of an iTENG using a highly mechanosensitive, visco‐poroelastic ion pump is suggested and the optimal characteristics of the polymer ion pump are reported by investigating optical, mechanical, electrical, and electrochemical properties. Surprisingly, the pressure sensitivity of the iTENG reaches 23.3 V kPa^?1, which is tens of times the record value. To achieve controlled high‐frequency pulses from an iTENG, kinematic systems using a gear train and a cam are integrated with a single grounded iTENG, which produces a maximum of 600 V and 22 mA (≈2.2 W cm^?2) at an input frequency of 1.67 Hz; after power transforming, those values are converted to 1.42 V and 225 mA. A capacitor of 1 mF can be fully charged to 2 V in only 60 s, making it possible to continuously operate a wireless‐communicating self‐powered humidity sensor. Also, due to the high transparency and deformability of the polymer ion pump, a self‐powered transparent tactile sensor is successfully assembled using a 5 × 5 iTENG array.     

Synthesis, crystal structure and properties of the novel chiral 3D coordination polymer with S-carboxymethyl-l-cysteine

Reaction of fresh Mn(OH)₂ precipitate and S-carboxymethyl-l-cysteine (H₂SCMC) in aqueous solution afforded a novel chiral 3D coordination polymer Mn(H₂O)(SCMC) 1, which crystallizes in the acentric polar space group P2₁ with cell constants a = 5.079(1) Å, b = 9.617(2) Å, c = 8.649(2) Å, β = 94.40(3)°, V = 421.2(1) Å³, Z = 2, and exhibit a SHG effect and ferroelectricity (a remnant polarization P_r = 0.0159 uC cm⁻², coercive field E_c = 0.83 kV cm⁻², saturation of the spontaneous polarization P_s = 0.234 uC cm⁻²). To the best of our knowledge, the present compound represents the first example of S-carboxymethyl-l-cysteine coordination polymers that exhibit possible ferroelectric behavior. The structural analysis revealed that the Mn²⁺ ions in 1 are each coordinated by one N atom and five O atoms of four S-carboxymethyl-l-cysteine ligand bridges four symmetry-related Mn²⁺ ions to form 3D MOF of 6⁶ topology type with irregular chiral channels extending along [1 0 0]. The temperature-dependent magnetic susceptibilities shows that 1 obeys Curie-Weiss law χ_m = C/(T − Θ) with C = 4.23 cm³ mol⁻¹ K and Θ = −5.86 K and the best fit gave a weak antiferromagnetic coupling (J = −0.282(5) cm⁻¹) among Mn ions.     

Structure and properties of cobalt ortho-phenylenediacetate coordination polymers with rigid dipyridyl ligands

Divalent cobalt coordination polymers containing both ortho-phenylenediacetate (ophda) and rigid dipyridyl ligands 4,4′-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethylene (dpee) display different topologies depending on carboxylate binding mode, tether length, and inclusion of charged species. [Co(ophda)(H₂O)(dpee)]_n (1) displays a common (4,4) grid layer motif. Use of the shorter bpy tether afforded {[Co₂(ophda)₂(bpy)₃(H₂O)₂][Co(bpy)₂(H₂O)₄](NO₃)₂·2bpy·7H₂O}_n (2) or [Co(ophda)(bpy)]_n (3) depending on cobalt precursor. Compound 2 manifests 5-connected [Co₂(ophda)₂(bpy)₃(H₂O)₂]_n pillared bilayer slabs with rare 4⁸6² SnS topology and entrained [Co(bpy)₂(H₂O)₄]²⁺ complex cations. The 3-D coordination polymer 3 has an uncommon 4,6-connected binodal (4⁴6²)(4⁴6¹⁰8) fsc topology, and shows ferromagnetic coupling (J = +1.5(2) cm⁻¹) along 1-D spiro-fused [Co(OCO)₂]_n chain submotifs.     

Polymeric and Compositional Properties of Novel Extracellular Microbial Polyglucosamine Biopolymer from New Strain of Citrobacter sp. BL-4

A novel polyglucosamine polymer, PGB-2, was produced extracellularly from a new strain Citrobacter sp. BL-4 using pH-stat fed batch cultivation. It was composed of 97.3% glucosamine and 2.7% rhamnose; its average molecular weight, solubility in 2% acetic acid and viscosity were 20 kDa, 5 g l⁻¹ and 2.9 cps, respectively. FT-IR and ¹H NMR spectra of PGB-2 revealed a close identity with chitosan from crab shells. Received 20 September 2005; Revisions requested 6 October 2005; Revisions received 16 November 2005; Accepted 16 November 2005     

Temperature effect on the conversions of phthalato and maleato manganese(II) complexes with diamine ligands

1,10-Phenanthroline hydrogen phthalato manganese(II) dimer [Mn₂(Hphth)₂(phen)₄] · 2Hphth · 6H₂O (1), monomeric phenanthroline phthalato manganese(II) monomer [Mn(phth)(phen)₂(H₂O)] · 2.5H₂O (2), 2,2′-bipyridine phthalato manganese(II) polymer [Mn(phth)(bpy)(H₂O)₂]_n (3) and 1,10-phenanthroline maleato polymer [Mn(male)(phen)(H₂O)₂]_n · 2nH₂O (4) (H₂phth = o-phthalic acid, male = maleic acid, phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine) have been synthesized and characterized spectroscopically and structurally. Each Mn(II) atom in dimeric 1 is octahedrally coordinated by two oxygen atoms of phthalate anions and by two cis-phenanthroline ligands. The hydrogen phthalato anion bridges the Mn(II) ions through the deprotonated carboxyl groups, while the carboxylic acid group remains free. In the monomeric 2, the Mn(II) ion is octahedrally surrounded by four nitrogen atoms from two cis-phen ligands, one carboxyl oxygen from a monodentate phth ion, and one coordinated water molecule. The dimeric phthalato complex 1 can be cleaved into monomer 2 under heating with deprotonation, and the course of the reaction can be qualitatively traced by IR spectra. The phthalate group in the complex 3 binds to two manganese atoms through the vicinal carboxyl-oxygen atoms in syn-syn bridging mode. The Mn(II) atoms are linked by the phthalate group to yield a one-dimensional chain running along the a-axis. The coordination polymer 3 can be obtained from the reaction of dichloro dibipyridine manganese with phthalate under heating. In polymer 4, the manganese atom is six-coordinated by two nitrogen atoms from phen, two oxygen atoms from the coordinated water molecules and two oxygen atoms from two different maleate dianions. Each maleato unit links two neighboring manganese atoms to yield one-dimensional chain along b-axis in bis-monodentate mode. The single-chain polymer 4 prepared at low temperature can be converted to double-chain coordination polymer [Mn(male)(phen)]_n · nH₂O (5) with dehydration in warm solution.     

Relating Recombination,Density of States,and Device Performance in an Efficient Polymer:Fullerene Organic Solar Cell Blend

We explore the interrelation between density of states, recombination kinetics, and device performance in efficient poly[4,8‐bis‐(2‐ethylhexyloxy)‐benzo[1,2‐b:4,5‐b']dithiophene‐2,6‐diyl‐alt‐4‐(2‐ethylhexyloxy‐1‐one)thieno[3,4‐b]thiophene‐2,6‐diyl]:[6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PBDTTT‐C:PC₇₁BM) bulk‐heterojunction organic solar cells. We modulate the active‐layer density of states by varying the polymer:fullerene composition over a small range around the ratio that leads to the maximum solar cell efficiency (50–67 wt% PC₇₁BM). Using transient and steady‐state techniques, we find that nongeminate recombination limits the device efficiency and, moreover, that increasing the PC₇₁BM content simultaneously increases the carrier lifetime and drift mobility in contrast to the behavior expected for Langevin recombination. Changes in electronic properties with fullerene content are accompanied by a significant change in the magnitude or energetic separation of the density of localized states. Our comprehensive approach to understanding device performance represents significant progress in understanding what limits these high‐efficiency polymer:fullerene systems.