Spectral redistribution of waveguided emission in BEH-PPV films

We report on spectral redistribution of the photoluminescence (PL) emission from the edge of thin-film planar waveguides of the conjugated polymer BEH-PPV [Poly(2,5-bis(2'-ethyl-hexyl)-1,4-phenylenevinylene] induced by self-absorption in the polymer film. The PL spectra present drastic changes and displace to longer wavelengths with increasing self-absorption. We observe an enhancement of the absolute PL intensity at longer wavelengths, which was interpreted as due to re-emission of self-absorbed photons. The significant efficiency for the PL re-emission suggests the use of self-absorption as a mechanism for tuning the emission into the near infrared.

Photophysics of conjugated polymers: interplay between Forster energy migration and defect concentration in shaping a photochemical funnel in PPV

Recent single molecule experiments have suggested the existence of a photochemical funnel in the photophysics of conjugated polymers, like poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] (MEH-PPV). The funnel is believed to be a consequence of the presence of conformational or chemical defects along the polymer chain and efficient non-radiative energy transfer among different chromophore segments. Here we address the effect of the excitation energy dynamics on the photophysics of PPV. The PPV chain is modeled as a polymer with the length distribution of chromophores given either by a Gaussian or by a Poisson distribution. We observe that the Poisson distribution of the segment lengths explains the photophysics of PPV better than the Gaussian distribution. A recently proposed version of an extended particle-in-a-box' model is used to calculate the exciton energies and the transition dipole moments of the chromophores, and a master equation to describe the excitation energy transfer among different chromophores. The rate of energy transfer is assumed to be given here, as a first approximation, by the well-known Forster expression. The observed excitation population dynamics confirms the photochemical funneling of excitation energy from shorter to longer chromophores of the polymer chain. The time scale of spectral shift and energy transfer for our model polymer, with realistic values of optical parameters, is in the range of 200-300 ps. We find that the excitation energy may not always migrate towards the longest chromophore segments in the polymer chain as the efficiency of energy transfer between chromophores depends on the separation distance between the two and their relative orientation.

Photophysics of PPV derivatives with varying conjugation lengths

Photoluminescence (PL), electroluminescence (EL) and photoconductivity (PC) of poly[(2,5-dimethoxy-p-phenylene) vinylene] (DMPPV) of varying conjugation length were studied. Thin film devices of the DMPPV with different conjugation lengths, as the active medium, were prepared. The PL emission spectra revealed the radiative decay of the singlet excitons with peak values corresponding to energies below the absorption onset. The PL. emission spectra of the copolymer films also revealed vibronic features, which get well resolved upon cooling to 80K, The devices exhibit light emitting diode (LED) behavior; the I-V curves and EL spectra are compared in these DMPPV samples having different conjugation lengths. The PC studies reveal subtle features, which can be attributed to the optically generated excitations in the system.

Symmetrized DMRG studies of low-energy electronic states of poly-para-phenylene (PPP) and poly-para-phenylenevinylene (PPV) systems

Symmetrized DMRG calculations on long oligomers of poly- para-phenylene (PPP) and poly-para-phenylene vinylene (PPV) systems within a `U-V' model have been carried out to obtain the one-photon, two-photon and singlet-triplet gaps in these systems. The extrapolated gaps (in eV) are 2.89, 3.76 and 2.72 in PPP and 3.01, 3.61 and 2.23 in PPV for the one- photon, two-photon and spin gaps respectively. By studying doped systems, we have obtained the exciton binding energies. The larger exciton binding energies, compared to strongly dimerized linear chains emphasizes the role of topology in these polymers. Bond orders, charge and spin correlations in the low-lying states bring out the similarities between the lowest one-photon, the lowest triplet and the lowest bipolaronic states in these systems. The two-photon state bond orders show evidence for strong localization of this excitation in both PPP and PPV systems.

MDMO-PPV包裹PbS量子点和纳米棒材料及电池的制备方法

于AD批量导入至AEzhangdi

Synthesis of MDMO-PPV capped PbS quantum dots and their application to solar cells

Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) capped PbS quantum dots about 3-6 nm in diameter were synthesized with a novel method. Unlike the synthesis of oleic acid capped PbS quantum dots, the reactions were carried out in solution at room temperature, with the presence of a capping ligand species, MDMO-PPV. The quantum dots were used to fabricate bulk heterojunction solar cells with an indium tin oxide (ITO)/polyethylenedioxythiophene/polystyrenesulphonate (PEDOT: PSS)/MDMO-PPV: PbS/Al structure. Current density-voltage characterization of the devices showed that after the addition of the MDMO-PPV capped PbS quantum dots to MDMO-PPV film, the performance was dramatically improved compared with pristine MDMO-PPV solar cells. (C) 2008 Elsevier Ltd. All rights reserved.

The synthesis of MDMO-PPV capped PbS nanorods and their application in solar cells

Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) capped PbS nanorods about 100 nm in diameter and 400 nm in length were synthesized via a hydrothermal route in toluene and dimethylsulfoxide solution. By blending the PbS nanorods with the MDMO-PPV as the active layer, bulk heterojunction solar cells with an indium tin oxide (ITO)/polyethylenedioxythiophene/polystyrenesulphonate (PEDOT PSS)/MDMO-PPV PbS nanorods/Al structure were fabricated in a N-2 filled glove box, Current density-voltage characterization of the devices showed that the solar cells with PbS nanorods hybrid with MDMO-PPV as active layer were better in performance than the devices with the polymer only. (C) 2009 Elsevier B.V. All rights reserved.

Organic/inorganic hybrid solar cells based on SnS/SnO nanocrystals and MDMO-PPV

SnS/SnO heterojunction structured nanocrystals with zigzag rod-like connected morphology were prepared by using a simple two-step method. Bulk heterojunction solar cells were fabricated using the SnS/SnO nanocrystals blended with poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV) as the active layer. Compared with solar cells using SnS nanoparticles hybridized with MDMO-PPV as the active layer, the SnS/SnO devices showed better performance, with a power conversion efficiency higher by about one order in magnitude.

含空穴传输基团PPV的合成与性能研究

该论文以提高聚苯撑乙烯（PPV）类发光聚合物的空穴传输性能为主要目的,通过将具有较高空穴传输能力的芳胺类小分子基元引入发光聚合物分子链,设计并合成了一系列含芳胺基元的PPV聚合物.另外,还通过对分子结构进行设计和控制,获得了红绿蓝三基色发光.最后还利用在共轭分子主链上引入具有三维空间位阻的侧链基团,获得了高效率的绿色发光聚合物材料.

PPV齐聚物为基元的发光材料的合成与性能研究

PPV齐聚物（OPV）因为具有确定的发光结构，高的发光效率，和光电活性，被广泛的关注。本论文本围绕PPV齐聚物（OPV）展开研究。设计合成了有机／无机杂化型和热交联型高分子发光材料，解决了制作多层器件过程中，旋涂时下面的薄膜容易被溶解的问题。我们设计合成了一系列能量转移和传输平衡型高分子发光材料，并对材料进行了优化。1、利用末端带活性双酚的OPV与二甲基二苯胺基硅烷通过熔融缩聚反应，合成出以硅氧烷为嵌段单元的发光聚合物，并通过调节OPV单体上的取代基团实现聚合物的蓝光发射。2、在PPV的末端引入可交联的苯乙烯基元，在高温下实现PPV的交联，得到了耐溶剂的PPV薄膜，利用其耐溶剂的特点用简单的旋涂的方法制备了双层器件，与单层器件相比效率提高了约13倍，器件的最大亮度达7O0cd／m2。3、通过化学修饰在OPV的两端引入了活性的三乙氧基硅烷，利用三乙氧基硅的反应活性，将OPV通过Sol-Gd的方法固定到SiO2的基质中，OPV与基质之间的作用为化学键，这样有效的减少了OPV在基质中的聚集。同时我们制备了PMMA与OPV通过物理共混得到的Si-OPV/PMMA薄膜和不带活性基团的Me-OPV，通过Sol-Gel制备了Me-OPV／SiO2薄膜，结果表明，采用物理掺杂时，客体OPV在主体中存在明显的聚集；经过热处理后只有化学掺杂的薄膜形态和光谱仍然保持稳定。4、将两种不同的OPV发光单元通过稳定的芳醚键连接，得到了热稳性的聚合物，由于不同的发光单元之间的吸收和发射光谱存在重叠，我们观察到分子内的能量转移现象，通过能量转移提高了聚合物在薄膜和溶液下的量子效率和相应的电致发光效率。5、为了改善PPV类能量转移型发光分子的传输特性，通过Wittig反应在聚合物主链中引入了电子传输单元：噁二唑，三唑。为了优化材料我们调节了传输单元在主链中的含量，通过器件数据优化出电子传输基元在主链中的最佳含量。使得优化后的材料的器件效率比未引入传输单元的提高了10倍以上，最大亮度达到1300cd／m2。

High PL-efficiency ZnO nanocrystallites/PPV composite nanofibers

In this paper, we report for the first time on the synthesis of ZnO nanocrystallites in conjugated polymer (PPV) nanofibers by the coupling of the in situ/blend methods and electrospinning. These composite nanofibers were characterized by fluorescence microscopy, atomic force microscope (AFM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD).

Synthesis, characterization, and electroluminescence of PPV copolymers containing electron and hole-transporting units

Three series of poly(phenylene vinylene) (PPV) derivatives containing hole-transporting triphenylamine derivatives [N-(4-octoxylphenyl)diphenylamine, N,N'-di(4-octyloxylphenyl)-N,N'-diphenyl-1,4-phenylenediamine, and N,N'-di(4-octoxylphenyl)-N,N'-diphenylbenzidine] (donor) and electron-transporting oxadiazole unit (2,5-diphenyl-1,3,4-oxadiazole) (acceptor) in the main chain were synthesized by improved Wittig copolymerization. The resulting donor-acceptor (D-A) polymers are readily soluble in common organic solvents, such as chloroform, dichloroethane, THF, and toluene.