Silver nanoplates formed at the air/water and solid/water interfaces

Silver nanoparticles and nanoplates were prepared at the air/AgNO₃ aqueous solution interfaces under poly(9-vinylcarbazole) (PVK) monolayers when illuminated by UV-light at room temperature and elevated temperatures, respectively. When the illuminated films at the air/water interfaces were covered by carbon-coated copper grids, nanoplates were formed even at room temperature, and the size of the nanoplates was much larger than those formed at the air/water interface under the same experimental conditions, indicating that copper took part in the formation of Ag nanoplates through the galvanic displacement reaction between Cu and Ag⁺ ions with the help of carbon layer to conduct electrons. It was found that the basal plane of these nanoplates is the (1 1 1) face of a face-centered cubic (fcc) Ag crystal. Although platelike structure can be formed at the carbon-coated copper grid/AgNO₃ aqueous solution interface without PVK film, it shows different features from those with PVK films, indicating that PVK film plays an important role in the formation of regular large nanoplates. Further observations indicate that special restrained microenvironment, adsorption of PVK molecules on a specific crystal face, anisotropic growth and attachment of the nanoparticles are responsible for the formation of the nanoplates.     

8－羟基喹啉铝掺杂聚乙烯基咔唑薄膜的光致发光及电致发光

８－羟基喹啉铝掺杂聚乙烯基咔唑薄膜的光致发光及电致发光马於光,唐建国,沈家骢,刘式墉（吉林大学分子光谱与分子结构开放实验室,集成光电子学国家联合重点实验室,长春,１３００２３）关键词聚合物,光致发光,电致发光,８－羟基喹啉铝某些有机染料作为波长转换介...     

PHOTOCONDUCTIVE PROPERTIES OF PVK:Alq3 BLEND FILMS STUDIED BY STEADY-STATE AND TIME-RESOLVED TRANSIENT PHOTOCURRENT SPECTRA

The carrier transport properties of the blends of the hole transport material poly(N-vinylcarbazole) (PVK) and the electron transport material tris (8-hydroxyquinolinolato) aluminumⅢ(Alq_3) are investigated at room temperature using steady-state and time-resolved transient photocurrent measurements as a function of doping concentration of Alq_3.Due to lower LUMO and higher HOMO energy level of Alq_3 than those of PVK,Alq_3 molecules may act as carrier trap states in PVK films at low concentration.However...     

EMISSION CHARACTERISTICS OF ORGANIC LIGHT-EMITTING DIODES WITH A HETEROSTRUCTURE OF DYE DOPED POLY(N-VINYLCARBAZOLE)/TRIS(8-HYDROXYQUINOLINE) ALUMINUM*

Organic electroluminescent diodes with a heterostructure of 9,10-bis(phenylethnyl) anthracene(BPEA) doped poly(N-vinylcarbazole) (PVK)/tris(8-hydroxyquinoline)aluminum (Alq_3) have beenfabricated. The electroluminescence (EL) both from BPEA and Alq_3 were observed when the Alq_3 layer isthin enough. With increasing thickness of the Alq_3 layer, the relative emission intensity of BPEA is graduallydecreased. For the thin Alq_3 layer structure, the light emission of Alq_3 becomes more dominant as the appliedvoltage increases. It is proposed that the electron-hole recombination takes place in both PVK and Alq_3 films.The field-induced quenching theory has also been applied to explain the change of the EL spectra withapplied voltage.     

Electroplex emission from a blend of poly(N-vinylcarbazole) and 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline

The PL and EL spectra of poly(N-vinylcarbazole) (PVK) : 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP) (1:1 w/w) film were found completely different. The PL spectrum is a single peak at 415 nm that originates from excitons emission from PVK, and the tail of the spectrum is suggested to be excimer emission from BCP molecules. However, a new emission at 595 nm was found in the EL spectra of devices ITO/PEDOT:PSS(50 nm)/PVK:BCP(1:1)(100 nm)/Al. After aggregate, exciplex and product of electrochemical reaction were ruled out, the new emission was proposed to be electroplex emission that occurred between PVK and BCP molecules. Under high voltage, only electroplex emission can be observed in the EL spectra.     

Photoluminescence and Electroluminescence Properties of 2,5-Bis[2,2′-bis(5-phenyl)-1,3,4-oxadiazole] Thiophene(T-OXD)and T-OXD/Poly(9-vinylcarbazole) Blends

The photoluminescence(PL) and the electroluminescence(EL) properties of a novel organic compound, 2,5-bis(2,2′-bis(5-phenyl)-1,3,4-oxadiazole(T-OXD), were studied in chloroform and in a solid thin film. The PL and the EL properties of T-OXD/poly(9-vinylcarbazole)(PVK) blends were also studied, which contained various contents of T-OXD. The PL maximum emission peaks of T-OXD/PVK blends show gradual bathochromtic-shift with the increase of the T-OXD content. The EL spectra of T-OXD/PVK devices are similar to their PL spectra, and all the EL maximum emission peaks show bathochromtic-shift compared with the corresponding PL spectra, which is ascribed to the formation of electroplex. The turn-on voltages for ITO/T-OXD:PVK/Al devices decreased from 13.5 V of the device cotaining 0.1% T-OXD(mass fraction) to 5 V of the device containing 5% T-OXD, which suggests that T-OXD improves the energy level match between T-OXD and PVK and enhances the emission efficiency. The experimental results indicate that T-OXD can be used as a good electron transporting material.     

PVK与新型D-π-A分子掺杂体系的能量转移及发光性质

通过对PVK与4种新型D-π-A分子(分别简写为CKD, TKD, PKD, NKD)掺杂体系的吸收光谱、激发光谱和光致发光光谱的研究, 分析了掺杂体系的光致发光特性和能量转移现象. 制备了结构为ITO/PEDOT/PVK∶D-π-A ω/Alq3/Al的电致发光器件, 研究了掺杂体系的电致发光性能. 研究结果表明, 通过改变D-π-A分子中不同给电子能力的电子给体, 可以调控其带隙, 进而实现对D-π-A分子发光峰位的调节; 给电子基团空间立构效应越高, 其荧光量子效率越高. 在掺杂体系的光致发光和电致发光中, PVK与D-π-A分子之间都发生了有效的能量转移, 通过调节PVK与D-π-A分子的比例, 可以调节掺杂体系的发光性能. 当TKD在PVK中的掺杂质量分数为6％时, 电致发光器件发光亮度为729.1 cd/m2时, 发光效率达到1.75 cd/A.     

Gold and silver nanorings formed at the air/water interface

Gold nanorings were prepared at the air/water interface through reduction of AuCl₄⁻ ions by UV-light irradiation or formaldehyde gas treatment at room temperature templated by thin films of phthalocyanine derivatives. Silver nanorings were produced at the air/water interface via reduction of Ag⁺ ions by UV-light irradiation templated by poly(9-vinylcarbazole) (PVK) thin films. These nanostructures were investigated by transmission electron microscopy (TEM), selective-area electron diffractometry (SAED), and high-resolution TEM (HRTEM). It was found that the gold nanorings are composed of close-packed nanoplates whose (1 1 0) crystal planes are parallel to the air/water interface; while silver rings are composed of nanoparticles. It is demonstrated that the ring-like aggregates formed by parallel linear supramolecules of the phthalocyanine derivatives and the ring-like structure of PVK supramolecules are responsible for the formation of the gold and silver nanorings, respectively.     

ToF-SIMS imaging of the nanoscale phase separation in polymeric light emitting diodes: effect of nanostructure on device efficiency

The nanostructure of the light emissive layer (EL) of polymer light emitting diodes (PLEDs) was investigated using force modulation microscopy (FMM) and scanning time-of-flight secondary ion mass spectrometry (ToF-SIMS) excited with focused Bi(3)(2+) primary beam. Three-dimensional nanostructures were reconstructed from high resolution ToF-SIMS images acquired with different C(60)(+) sputtering times. The observed nanostructure is related to the efficiency of the PLED. In poly(9-vinyl-carbazole) (PVK) based EL, a high processing temperature (60 °C) yielded less nanoscale phase separation than a low processing temperature (30 °C). This nanostructure can be further suppressed by replacing the host polymer with poly[oxy(3-(9H-9-carbazol-9-ilmethyl-2-methyltrimethylene)] (SL74) and poly[3-(carbazol-9-ylmethyl)-3-methyloxetane] (RS12), which have similar chemical structures and energy levels as PVK. The device efficiency increases when the phase separation inside the EL is suppressed. While the spontaneous formation of a bicontinuous nanostructure inside the active layer is known to provide a path for charge carrier transportation and to be the key to highly efficient polymeric solar cells, these nanostructures are less efficient for trapping the carrier inside the EL and thus lower the power conversion efficiency of the PLED devices.     

Charge transfer polycondensation of diethyl chelidonate with diamines in the presence of polyvinylcarbazole

Polycondensation of diethyl chelidonate (DEC), which contains an electron-accepting γ-pyrone nucleus, with hexamethylenediamine (HMD) takes place easily even at room temperature to form a corresponding polyamide. Since DEC was expected to form a charge transfer complex with an electron-donating compound such as polyvinylcarbazole (PVK), the polycondensation of DEC with diamines was carried out in the presence of PVK as a matrix. It was found that the rate of the polycondensation of DEC with diamines in dioxane was enhanced either by the presence of PVK or by the irradiation with ultraviolet (UV) light. Moreover, the polycondensation of DEC with HMD in the presence of PVK was accelerated by the UV irradiation, probably owing to the transfer of light energy.     

内含C60掺杂空穴传输层的量子点电致发光器件

聚乙烯咔唑（PVK）中掺入富勒烯（C₆₀）的重量比从0%到10%变化,以研究在空穴传输层中掺杂C₆₀后对量子点电致发光器件性能的影响。掺入C₆₀后的PVK薄膜在氧化铟锡（ITO）基底上均方根粗糙度从3nm降至1.6nm。另外,掺入C₆₀后有利于空穴的注入和传输,改善器件中电子和空穴的平衡,提高了器件的效率。     

Electroluminescent Properties of an Electrochemically Cross‐Linkable Carbazole Peripheral Poly(Benzyl Ether) Dendrimer

The electroluminescent (EL) properties of a cross‐linkable carbazole‐terminated poly(benzyl ether) dendrimer, G₃‐cbz DN, doped into a PVK:PBD host matrix with a double‐layer device configuration are investigated. Different concentrations of the guest material can control device efficiency, related to chromaticity of white emission and the origin of excited‐state complexes occurring between hole‐transporting carbazole units (PVK or G₃‐cbz DN) and electron‐transporting oxadiazole (PBD). Two excited states (exciplex and electroplex) generated at the interfaces of PVK/G₃‐cbz DN and PBD result in competitive emission, exhibiting a broad band in the EL spectra.     

内含C_(60)掺杂空穴传输层的量子点电致发光器件

聚乙烯咔唑(PVK)中掺入富勒烯(C60)的重量比从0%到10%变化,以研究在空穴传输层中掺杂C60后对量子点电致发光器件性能的影响。掺入C60后的PVK薄膜在氧化铟锡(ITO)基底上均方根粗糙度从3 nm降至1.6 nm。另外,掺入C60后有利于空穴的注入和传输,改善器件中电子和空穴的平衡,提高了器件的效率。     

聚合物薄膜交流电致发光器件

We have demonstrated an electroluminescent (EL) device having the structure of ITO/PPV/Alq3:PVK/Al. This device could be driven by either forward bias or backward bias, and its EL originated from PPV layer.     

White light emission from single layer poly (n-vinylcarbazole) polymeric light-emitting devices by mixing singlet and triplet excimer emissions

White light electroluminescence (EL) was obtained by mixing emission from singlet and triplet excimers from a single poly (n-vinylcarbazole) (PVK) spin cast layer after irradiation of the solution with UV light. With increased UV light irradiation, the intensity from the triplet excimer (red-630 nm) of PVK increased compared with that of the singlet excimer (blue-460 nm) due to an increased population of both adjacent benzene rings being aligned with one another (fully overlapping) versus only one of the adjacent benzene rings being aligned (partially overlapping). The emission color changed from blue to white with increased UV irradiation time while the EL brightness and current density decreased and the turn-on voltage increased.     

On the triplet state of poly(N-vinylcarbazole)

Triplet state properties including transient triplet absorption spectrum, intersystem crossing yields in solution at room temperature and phosphorescence spectra, quantum yields and lifetimes at low temperature as well as singlet oxygen yields were obtained for poly(N-vinylcarbazole) (PVK) in 2-methyl-tetrahydrofuran (2-MeTHF), cyclohexane or benzene. The results allow the determination of the energy value for the lowest lying triplet state and also show that triplet formation and deactivation is a minor route for relaxation of the lowest excited singlet state of PVK. In addition, they show the triplet state is at higher energy than reported heavy metal dopants used for electrophosphorescent devices, such that if this is used as a host it will not quench their luminescence.     

Properties of chlorine-doped poly(N-vinylcarbazole) thin films

Thin films of poly(N-vinylcarbazole) (PVK) have been obtained by thermal evaporation under vacuum. The chain length of the polymer is shortened by this deposition technique, which induces a strong reactivity between chlorine and the PVK films. After chlorine doping, there is complex salt formation as shown by electron spin resonance spectroscopy (ESR) and X-ray photoelectron spectroscopy (XPS). However, the major part of the chlorine has reacted with PVK. The thermal evaporation induces amorphization of the PVK, while chlorine doping induces polymer degradation with NH₄Cl formation. Because of this degradation the carriers detected by ESR are strongly localized on carbazole radicals, thereby explaining the small increase in the conductivity of PVK films even after chlorine doping.     

Molecular simulation of excimer fluorescence in polystyrene and poly(vinylcarbazole)

In fluorescence emission spectra of poly(vinylcarbazole) (PVK), two types of excimers are observed, the fully and the partially overlapped excimers, namely, excimers and exciplexes. In this work, we investigated the structural changes induced by the transition between electronic levels S(0) and S(1). Furthermore, the widely used assumption of similar potential energy surfaces in the S(0) and S(1) states and its use in molecular dynamics simulations are thoroughly examined for PVK and polystyrene (PS). The ground-state and excited-state intermolecular potentials between phenyl or carbazyl substituents in PS or PVK, respectively, are computed from high-level ab initio calculations and fit to analytic potentials. Finally, molecular dynamics simulations are performed at room temperature for PS and for isotactic and syndiotactic PVK. This treatment enabled the decoupling of excimer and exciplex contributions from the simulated spectra.     

Direct electrochemical nanopatterning of polycarbazole monomer and precursor polymer films: ambient formation of thermally stable conducting nanopatterns

The direct nanopatterning of polycarbazole on ultrathin films of a "precursor polymer" and monomer under ambient conditions is reported. In contrast to previous reports on electrochemical dip-pen nanolithography using monomer ink or electrolyte-saturated films in electrostatic nanolithography, these features were directly patterned on spin-cast films of carbazole monomer and poly(vinylcarbazole) (PVK) under room temperature and humidity conditions. Using a voltage-biased atomic force microscope (AFM) tip, electric-field-induced polymerization and cross-linking occurred with nanopatterning in these films. Different parameters, including writing speed and bias voltages, were studied to demonstrate line width and patterning geometry control. The conducting property (current-voltage (I-V) curves) of these nanopatterns was also investigated using a conducting-AFM (C-AFM) setup, and the thermal stability of the patterns was evaluated by annealing the polymer/monomer film above the glass transition (T(g)) temperature of the precursor polymer. To the best of our knowledge, this is the first report in which thermally stable conducting nanopatterns were drawn directly on monomer or polymer film substrates using an electrochemical nanolithography technique under ambient conditions.     

Photoluminescence and electroluminescence of methoxy and carboethoxy derivatives of 1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline

A series of methoxy (MO) and carboethoxy (CE) derivatives of 1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline ([DPPQ]) are characterized by spectroscopic methods. All dyes show the photoluminescent spectra which are highly solvatochromic. In the case of 6MO[DPPQ] and 6CE[DPPQ] the emission bands are broad and shifted to the red with increasing of solvent polarity whereas the dyes 6MO1pMO[DPPQ] and 6MO13pMO[DPPQ] exhibit a reverse solvatochromism. The large difference between the excited- and state-dipole moments indicates a strong electron transfer effects in all dyes. The EL spectra are obtained for the fabricated OLEDs with a general structure of EL device ITO/PVK:6X[DPPQ]/Ca/Al. The blue emission originating from PVK host matrix appears to be quenched in EL spectra of doped PVK matrix giving rise to emission in blue, blue-green or green spectral regions. The obtained results demonstrate that a series of newly synthesized methoxy and carboethoxy [DPPQ]-derivatives may be considered as promising materials for electroluminescent applications.