P3HT修饰一维有序壳核式CdS/ZnO纳米棒阵列复合膜的光电化学性能

采用电化学方法在铟锡氧化物(ITO)导电玻璃上制备了高度有序的ZnO纳米棒阵列, 在ZnO纳米棒阵列上先后电化学沉积CdS纳米晶膜及聚3-己基噻吩(P3HT)薄膜得到P3HT修饰的一维有序壳核式CdS/ZnO纳米阵列结构, 并通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、能量散射X射线(EDX)等表征手段证实了该结构的形成. 以此纳米结构薄膜为光阳极组装新型半导体敏化太阳电池, 研究了CdS纳米晶膜的厚度和P3HT薄膜的沉积对电池光伏性能的影响, 初步探讨了电荷在电池结构中的传输机理, 结果表明, CdS纳米晶膜和P3HT薄膜的沉积有效地拓宽了光阳极的光吸收范围, 实验中电池的光电转换效率最高达到1.08%.     

Depth-resolved molecular structure and orientation of polymer thin films by synchrotron X-ray diffraction

An exemplary system suitable for optoelectronics applications, i.e. poly(3-hexylthiophene), hereinafter P3HT, deposited by spin casting onto silicon substrates functionalised by three selected molecules and then properly annealed, has been examined. Grazing Incidence X-ray Scattering (GIXS) measurements have been performed with 4-circle diffractometer, allowing for a fine control of sample axes movement.By choosing different grazing incident angles, diffraction patterns from different layers of polymeric thin films have been recorded. Both in-plane and out-of-plane geometries have been combined in order to obtain complementary structural information. In this way structural and orientational differences of the polymer along with the film thickness (?50 nm) have been highlighted. For all P3HT films spun on functionalized Si wafer, macromolecular layers close to the substrate surface give some evidence of higher order and orientation than those outmost the surface, and this behaviour is pronounced to a different extent depending on the functionalized molecules used. Contrariwise P3HT layers deposited onto bare Si wafer display reduced orientation and decreased crystallite size, especially at buried interface.     

Creating patterned carbon nanotube catalysts through the microcontact printing of block copolymer micellar thin films

We report a route for synthesizing patterned carbon nanotube (CNT) catalysts through the microcontact printing of iron-loaded poly(styrene-block-acrylic acid) (PS-b-PAA) micellar solutions onto silicon wafers coated with thin aluminum oxide (Al(2)O(3)) layers. The amphiphilic block copolymer, PS-b-PAA, forms spherical micelles in toluene that can form quasi-hexagonal arrays of spherical PAA domains within a PS matrix when deposited onto a substrate. In this report, we dip a poly(dimethylsiloxane) (PDMS) molded stamp into an iron-loaded micellar solution to create a thin film on the PDMS features. The PDMS stamp is then put in contact with a substrate, and uniaxial compressive stress is applied to transfer the micellar thin film from the PDMS stamp onto the substrate in a defined pattern. The polymer is then removed by oxygen plasma etching to leave a patterned iron oxide nanocluster array on the substrate. Using these catalysts, we achieve patterned vertical growth of multiwalled CNTs, where the CNTs maintain the fidelity of the patterned catalyst, forming high-aspect-ratio standing structures.     

Coating on a Cold Substrate Largely Enhances Power Conversion Efficiency of the Bulk Heterojunction Solar Cell

Spin‐coating a mixture solution of P3HT and PCBM on a cold substrate largely enhanced the power conversion efficiency (PCE) of the bulk heterojunction (BHJ) solar cells. This concept was based on the abrupt decrease in the solubility of P3HT as solution temperature decreased. The selective precipitation of P3HT on the PEDOT:PSS‐coated cold substrate facilitated a desirable rich composition of P3HT at the interface with the PEDOT:PSS layer. The high crystallinity of P3HT suppressed the movement of PCBM during thermal annealing, preventing aggregation of PCBM. The morphological excellence of the pristine film gave a comparable PCE to that made by the conventional fabrication process. After thermal annealing, the device made via coating on a cold substrate showed above 30% increase in PCE from the BHJ solar cells made by the conventional method.

     

Tuning of the charge and energy transfer in ternary CdSe/poly(3-methylthiophene)/poly(3-hexylthiophene) nanocomposite system

Composite CdSe:poly(3-methylthiophene) (P3MT) nanoparticles have been synthesized via polymerization of 3-methylthiophene (3MT) in the presence of CdSe particles of nanorod or dot-like morphology and dispersed in the poly(3-hexylthiophene) (P3HT) matrix. The effect of the P3MT layer to mediate charge and energy transfer between CdSe and P3HT in the ternary nanocomposite system has been studied using electronic absorption, photoluminescence spectroscopy, and current–voltage measurements. The energy level diagram of the composite system has been deduced based on optical and electrochemical data of the separate components of the system. The contribution of the low- and high-molecular fractions of P3MT to control the charge transfer in order to optimize the intermediary role of P3MT is analyzed. Particularly, it was shown that excitation of the low-molecular P3MT leads to energy transfer to both CdSe and P3HT components, and it also serves as a barrier against recombination of electrons and holes separated at CdSe and P3HT, respectively. Thus, the role of the P3MT interlayer in assisting the charge separation and increasing an open-circuit voltage in the photovoltaic cell based on the ternary system is demonstrated.     

Stamping patterns of insulated gold nanowires with self-organized ultrathin polymer films

A thermal contact transfer technique is presented for the fabrication of nanoscaled to microscaled patterns of polymer-insulated metal structures on ceramic surfaces using metal-coated, thermoplastic stamps. The thermally activated formation of polymer-metal-polymer (PMP) heterostructures occurs spontaneously when a metal-coated thermoplastic stamp is compressed against a ceramic substrate and subsequently heated. The presented technique exploits the dynamics of ultrathin polymer films localized at interfaces and interfacial forces to prompt local reorganization of polymer stamp materials during processing. Intercalation of polymer stamp materials into the metal-substrate interface yields a cohesive polymer layer that binds the metal layer to the substrate. Disproportionate adhesion between the bulk polymer and the polymer layer at the stamp-metal interface leaves a capping layer upon separation of the stamp from the substrate. Here we demonstrate this technique with single use, bilevel polymer stamps which afford transfer of two distinct general products. The transfer of insulated submicrometer wide wires from the raised stamp features affords patterns of trilayered PMP structures with uniform wire dimensions. Concomitant transfer from the recessed stamp features allows fabrication of multilayered PMP architectures with sub-100 nm spacing from microstructured polymer stamps. Thus, patterns with two different insulated nanowire widths are readily fabricated in a single stamping process. A variety of ceramic substrates, thermoplastic materials, and metals can be used; e.g., inexpensive gold-coated CD or DVD media can be used as stamps, where the combination of materials dictates the relative interfacial forces and the processing parameters.     

Light-induced degradation of the active layer of polymer-based solar cells

Polymer-based organic solar cells are known to offer a poor stability in real use conditions, and the photodegradation of the active organic layer plays an important role in the reduced lifetime of the devices. This paper focuses on the photodegradation of two conjugated polymers used in organic solar cells, namely poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene (MDMO-PPV) and poly(3-hexyylthiophene) (P3HT), and their blends with [60]PCBM (methano-fullerene[6,6]-phenyl C61-butyric acid methyl ester), a fullerene derivative. MDMO-PPV and P3HT thin films were submitted to photoageing (λ > 300 nm) in the presence and in the absence of oxygen. The mechanisms by which these polymers degrade were elucidated. P3HT, pristine and blended with PCBM, was shown to be much more stable under illumination than MDMO-PPV. The results showed that, if deposited on an inert substrate and well protected from oxygen with a convenient encapsulation, P3HT:PCBM based active layer should be intrinsically stable for several years in use conditions.     

Design of Well‐Defined Monofunctionalized Poly(3‐hexylthiophene)s: Toward the Synthesis of Semiconducting Graft Copolymers

The post‐functionalization of poly(3‐hexylthiophene) (P3HT) via various synthetic routes is reported. Well‐defined and monofunctionalized ω‐thiol‐terminated P3HT, ω‐carboxylic acid‐terminated P3HT, ω‐acrylate‐terminated P3HT, and ω‐methacrylate‐terminated P3HT are obtained in high yields through a straightforward procedure. From those, different novel P3HT‐based graft copolymers are synthesized following two routes: “grafting onto” and “grafting through” (macromonomer polymerization) methods. The synthesis of three types of graft copolymers is described. Each one has “rod” P3HT‐grafted side chains on a “coil” main chain, which can be polyisoprene, poly(vinyl alcohol), or poly(butyl acrylate). Each copolymer is characterized by size‐exclusion chromatography and NMR.     

Uniaxial alignment of poly(3-hexylthiophene) nanofibers by zone-casting approach

The preparation of large area coverage of films with uniaxially aligned poly(3-hexylthiophene)(P3HT) nanofibers by using zone-casting approach is reported.The length and the orientation of the nanofibers are defined by the solubility of the solvent,the P3HT molecular weight and the substrate temperature.The length of the oriented nanofibers could be increased from 1 μm to more than 10 μm by adding poor solvent into the P3HT solution.It is found that for P3HT of relatively low molecular weight,a solvent with relatively low solubility has to be chosen to get the oriented film.While for the high molecular weight P3HT,the solvent with a relatively high solubility has to be used.The well-aligned film could be obtained because of the solute concentration gradient in the region where the critical concentration is reached during the zone-casting process.Particularly,the solvent evaporation rate and crystallization rate must be chosen properly to satisfy the stationary conditions above,which were controlled by an appropriate choice of solvent and substrate temperature.The film prepared by zone-casting approach had microcrystalline P3HT domains with more inter-chain order than spin-coating film.Meanwhile,the P3HT π-π stacking direction was parallel to the alignment direction of the nanofibers.     

Complete plastic nanofluidic devices for DNA analysis via direct imprinting with polymer stamps

Development of all polymer-based nanofluidic devices using replication technologies, which is a prerequisite for providing devices for a larger user base, is hampered by undesired substrate deformation associated with the replication of multi-scale structures. Therefore, most nanofluidic devices have been fabricated in glass-like substrates or in a polymer resist layer coated on a substrate. This letter presents a rapid, high fidelity direct imprinting process to build polymer nanofluidic devices in a single step. Undesired substrate deformation during imprinting was significantly reduced through the use of a polymer stamp made from a UV-curable resin. The integrity of the enclosed all polymer-based nanofluidic system was verified by a fluorescein filling experiment and translocation/stretching of λ-DNA molecules through the nanochannels. It was also found that the funnel-like design of the nanochannel inlet significantly improved the entrance of DNA molecules into nanochannels compared to an abrupt nanochannel/microfluidic network interface.     

Fabrication of coaxial TiO2/Sb2S3 nanowire hybrids for efficient nanostructured organic-inorganic thin film photovoltaics

We report on low-cost, all solution fabrication of efficient air-stable nanostructured thin film photovoltaics comprised of n-type Sb(2)S(3) chemically deposited onto TiO(2) nanowire array films, forming coaxial Sb(2)S(3)/TiO(2) nanowire hybrids vertically oriented from the SnO(2):F coated glass substrate, which are then intercalated with poly(3-hexylthiophene) (P3HT) for hole transport and enhanced light absorption.     

Anisotropic Photoluminescence of Poly(3-hexyl thiophene) and Their Composites with Single-Walled Carbon Nanotubes Highly Separated in Metallic and Semiconducting Tubes

In this work, the effect of the single-walled carbon nanotubes (SWNTs) as the mixtures of metallic and semiconducting tubes (M + S-SWNTs) as well as highly separated semiconducting (S-SWNTs) and metallic (M-SWNTs) tubes on the photoluminescence (PL) of poly(3-hexyl thiophene) (P3HT) was reported. Two methods were used to prepare such composites, that is, the chemical interaction of the two constituents and the electrochemical polymerization of the 3-hexyl thiophene onto the rough Au supports modified with carbon nanotubes (CNTs). The measurements of the anisotropic PL of these composites have highlighted a significant diminution of the angle of the binding of the P3HT films electrochemical synthetized onto Au electrodes covered with M + S-SWNTs. This change was attributed to metallic tubes, as was demonstrated using the anisotropic PL measurements carried out on the P3HT/M-SWNTs and P3HT/S-SWNTs composites. Small variations in the angle of the binding were reported in the case of the composites prepared by chemical interaction of the two constituents. The proposed mechanism to explain this behavior took into account the functionalization process of CNTs with P3HT. The experimental arguments of the functionalization process of CNTs with P3HT were shown by the UV-VIS-NIR and FTIR spectroscopy as well as surface-enhanced Raman scattering (SERS). A PL quenching process of P3HT induced both in the presence of S-SWNTs and M-SWNTs was reported, too. This process origins in the various de-excitation pathways which can be developed considering the energy levels diagram of the two constituents of each studied composite.     

Microcontact printing of Alzheimer’s β-amyloid monomers and fibrils

Adsorption of the 40-residue Alzheimer’s β-amyloid peptide (Aβ40) on a hydrophobic surface leads to formation of potentially disease-relevant aggregates. Existing techniques are limited in characterizing the adsorbed Aβ40 and producing potentially useful Aβ40 microstructures such as microarrays and microparticles. In this paper, a novel approach based on microcontact printing (μCP) to studying and utilizing adsorption of Aβ40 monomers and fibril fragments on hydrophobic surface of polydimethylsiloxane (PDMS) stamps has been developed. By transferring the adsorbed layer from the stamp to a glass substrate, this approach allows easy measurement of thickness of the adsorbed layer. It also enables characterization of the face of the adsorbed layer in contact with the stamp surface. This face exhibits significant higher thioflavin T fluorescence than the face exposed to water, suggesting β-sheet formation induced by the PDMS surface. The intrinsic stability of the adsorbed layer is evaluated by printing the layer on a water-soluble substrate and exposing it to water vapor or water. Stable particulate microstructures in water are obtained by chemically crosslinking the adsorbed peptides. Moreover, co-micropatterning of the different states of Aβ40 (monomers and fibril fragments) is demonstrated. This μCP-based approach is simple, versatile, and holds potential for various applications.     

Investigation of the Effect of Thermal Annealing on Poly(3‐hexylthiophene) Nanofibers by Scanning Probe Microscopy: From Single‐Chain Conformation and Assembly Behavior to the Interfacial Interactions with Graphene Oxide

Poly(3‐hexylthiophene) (P3HT) has been widely used in devices owing to its excellent properties and structural features. However, devices based on pure P3HT have not exhibited high performance. Strategies, such as thermal annealing and surface doping, have been used to improve the electrical properties of P3HT. In this work, different from previous studies, the effect of thermal annealing on P3HT nanofibers are examined, ranging from the single polymer chain conformation to chain packing, and the interfacial interactions with graphene oxide (GO) at nanoscale dimensions, by using scanning tunneling microscopy (STM), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). High‐resolution STM images directly show the conformational changes of single polymer chains after thermal annealing. The morphology of P3HT nanofibers and the surface potential changes of the P3HT nanofibers and GO is further investigated by AFM and KPFM at the nanoscale, which demonstrate that the surface potentials of P3HT decrease, whereas that of GO increases after thermal annealing. All of the results demonstrate the stronger interfacial interactions between P3HT and GO occur after thermal treatments due to the changes in P3HT chain conformation and packing order.     

Organic-inorganic nanocomposites via directly grafting conjugated polymers onto quantum dots

Nanocomposites of poly(3-hexylthiophene)-cadmium selenide (P3HT-CdSe) were synthesized by directly grafting vinyl-terminated P3HT onto [(4-bromophenyl)methyl]dioctylphosphine oxide (DOPO-Br)-functionalized CdSe quantum dot (QD) surfaces via a mild palladium-catalyzed Heck coupling, thereby dispensing with the need for ligand exchange chemistry. The resulting P3HT-CdSe nanocomposites possess a well-defined interface, thus significantly promoting the dispersion of CdSe within the P3HT matrix and facilitating the electronic interaction between these two components. The photophysical properties of nanocomposites were found to differ from the conventional composites in which P3HT and CdSe QDs were physically mixed. Solid-state emission spectra of nanocomposites suggested the charge transfer from P3HT to CdSe QDs, while the energy transfer from 3.5 nm CdSe QD to P3HT was implicated in the P3HT/CdSe composites. A faster decay in lifetime further confirmed the occurrence of charge transfer in P3HT-CdSe nanocomposites.     

Polymer-Based Superhydrophobic Coating Fabricated from Polyelectrolyte Multilayers of Poly(allylamine hydrochloride) and Poly(acrylic acid)

Superhydrophobic films mainly based on poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) polyelectrolyte multilayer have been deposited onto cleaned glass substrate by a layer-by-layer dip coating method. 3 bilayers of the PAH and PAA was directly coated onto the substrate as an underlying layer for subsequent coating. Desired surface roughness on the polyelectrolyte bilayers was created by etching the bilayers in hydrochloric acid solution so as to create the open pore having suitable size at the surface. Then, nanoparticles such as SiO₂ and TiO₂ of various sizes were deposited onto the etched polyelectrolyte bilayers. Finally, the surfaces were further modified with semifluorinated silane followed by cross-linking at 180 °C for 2 h to obtain desirable surface morphological features. The effect of etching time and addition of nanoparticles on surface morphology was investigated using an atomic force microscope (AFM). Wetting ability of the prepared film was determined by measuring water droplet contact angle using a goniometer. Adhesion between the superhydrophobic films and the substrate was evaluated by using a standard tape test method (D3359). The adhesion was improved by reducing the organic content in the films.     

聚(3-己基噻吩)作为光谱增感层在有机太阳电池光谱响应增强中的应用

报道了利用聚(3-己基噻吩)(P3HT)作为前置缓冲层来弥补(4,8-双-(2-乙基己氧基)-苯并[1,2-b:4,5-b']二噻吩)-(4-氟代噻并[3,4-b]噻吩(PBDT-TT-F):[6,6]-苯基-C₆₁-丁酸甲酯(PC₆₁BM)共混体相异质结(BHJ)电池对450-600 nm处光谱响应不足的新的器件结构设计思路. 光谱带隙为1.8 eV的PBDT-TT-F 在550-700 nm处有很强的光谱吸收, 在有机太阳电池器件上有很好的应用潜能. 但其在350-550 nm处的吸收不强, 影响了器件对太阳光谱的利用效率. 与此相比, P3HT薄膜的光谱吸收主要在450-600 nm范围内, 同PBDT-TT-F 形成良好的互补关系. 新设计的器件外量子效率(EQE)研究结果表明, 利用P3HT 作为前置缓冲层可以与PBDT-TT-F:PC₆₁BM薄膜中的PC₆₁BM形成平面异质结, 从而拓展了器件在450-600 nm处的光谱响应范围,实现光谱增感作用. 优化P3HT的厚度为20 nm左右, 器件对外输出的短路光电流密度从11.42 mA·cm^-2提高到12.15 mA·cm^-2, 达到了6.3%的提升.     

Layer-by-layer assembled multilayer TiO(x) for efficient electron acceptor in polymer hybrid solar cells

We demonstrate that TiO(x) nanocomposite films fabricated using electrostatic layer-by-layer (LbL) assembly improve the power conversion efficiency of photovoltaic cells compared to conventional TiO(x) films fabricated via the sol-gel process. For this study, titanium precursor/poly(allylamine hydrochloride) (PAH) multilayer films were first deposited onto indium tin oxide-coated glass to produce TiO(x) nanocomposites (TiO(x)NC). The specific effect of the LbL processed TiO(x) on photovoltaic performance was investigated using the planar bilayer TiO(x)NC and highly regioregular poly(3-hexylthiophene) (P3HT) solar cells, and the P3HT/LbL TiO(x)NC solar cells showed a dramatic increase in power efficiency, particularly in terms of the short current density and fill factor. The improved efficiency of this device is mainly due to the difference in the chemical composition of the LbL TiO(x)NC films, including the much higher Ti(3+)/Ti(4+) ratio and the highly reactive facets of crystals as demonstrated by XPS and XRD measurement, thus enhancing the electron transfer between electron donors and acceptors. In addition, the grazing incidence wide-angle X-ray scattering (GIWAXS) study revealed the presence of more highly oriented P3HT stacks parallel to the substrate on the LbL TiO(x)NC film compared to those on the sol-gel TiO(x) films, possibly influencing the hole mobility of P3HT and the energy transfer near and at the interface between the P3HT and TiO(x) layers. The results of this study demonstrate that this approach is a promising one for the design of hybrid solar cells with improved efficiency.     

P3HT stripe structure with oriented nanofibrils enabled by controlled inclining evaporation

The preparation of the poly(3-hexylthiophene) (P3HT) stripe structure with oriented nanofibrils prepared by controlled inclining evaporative technique is reported. The distance of the adjacent stripes could be controlled from 40 μm to 100 μm by decreasing the inclining angle. The oriented nanofibrils in the stripes can be obtained because the P3HT lamellae diffuse directionally and form 1D crystals at the three-phase contact line of the drop. In order to get the oriented P3HT stripes, the proper solvent evaporation rate which is controlled by the inclining angle and the wettability of the substrate must be carefully chosen to match the P3HT 1D crystallization rate. It is found that large inclining angle and the hydrophilic substrate (for example: glass and PEDOT) are beneficial to get P3HT stripe structure with oriented nanofibrils.