Spectroscopic and electrical properties of 3-alkyl pyrrole-pyrrole copolymers

Three types of copolymers composed of pyrrole and 3-alkyl pyrroles (with alkyl being pentyl, nonyl and undecyl) have been synthesized. A strong linear dependency of the alkyl chain length on the as-prepared copolymer physical properties is demonstrated via (a) DSC (for phase transition temperatures and enthalpy changes) and (b) UV-vis (for wavelengths of the polaronic and bipolaronic electronic transitions, and ratio of the corresponding absorbances). A trend in the copolymers' doping level vs alkyl chain length is also estimated, via IR, by taking the ratio of band intensities of the stretching modes of the polaronic and bipolaronic species. The copolymers are found to be soluble in organic solvents and their solutions can be cast onto glass substrates or metals resulting in thin films, which can be used as the electroactive component of Schottky diodes. The electrical properties of these diodes are also found to be dependent on increasing 3-alkyl chain length.     

Time-Resolved Structural Kinetics of an Organic Mixed Ionic–Electronic Conductor

The structure and packing of organic mixed ionic–electronic conductors have an especially significant effect on transport properties. In operating devices, this structure is not fixed but is responsive to changes in electrochemical potential, ion intercalation, and solvent swelling. Toward this end, the steady-state and transient structure of the model organic mixed conductor, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), is characterized using multimodal time-resolved operando techniques. Steady-state operando X-ray scattering reveals a doping-induced lamellar expansion of 1.6 Å followed by 0.4 Å relaxation at high doping levels. Time-resolved operando X-ray scattering reveals asymmetric rates of lamellar structural change during doping and dedoping that do not directly depend on potential or charging transients. Time-resolved spectroscopy establishes a link between structural transients and the complex kinetics of electronic charge carrier subpopulations, in particular the polaron–bipolaron equilibrium. These findings provide insight into the factors limiting the response time of organic mixed-conductor-based devices, and present the first real-time observation of the structural changes during doping and dedoping of a conjugated polymer system via X-ray scattering.     

顺式聚乙炔中的次近邻电子相互作用

采用数值计算的方法,研究了次近邻电子跳跃作用对顺式聚乙炔(Cis-PA)的能谱、电子束缚态和双极化子附近的二维局域振动模的影响．与基本哈密顿的计算结果比较发现：Cis-PA能谱的电子-空穴对称性被解除,与实验结果相吻合;各种激发态的电子束缚态数目发生了改变,双极化子晶格附近的局域模的频率和数目都与次近邻电子跳跃作用有关．     

Mobile Bipolaron—Strong Coupling Approach

We explore the properties of the bipolaron in a 1D Holstein–Hubbard model with dynamical quantum phonons. We apply strong coupling theory to investigate the intersite bipolaron. We investigate the influence of the Hubbard interaction on the bipolaron binding energy, effective mass, and phase diagram. We compare our analytic results to recent numerical calculations [1]. In the intermediate and strong coupling regimes, a bipolaron is stable beyond the naive stability limit U ₀ = 2g ². The intersite bipolaron has a significantly reduced mass compared to the single site bipolaron, and is stable in the strong coupling regime up toU _c 4g ².     

掺杂PVK薄膜的荧光谱及掺杂机制

根据ＰＶＫ掺杂后荧光谱的改变,提出了ＰＶＫ掺杂的掺杂机制,沿ＰＰＶ链是极化子和双极化子态,而链间是由于双极化子的跃迁。实践结果与模型相符。     

Study of polaron and bipolaron states in polypyrrole by in situ Raman spectroelectrochemistry

The transitions from the reduced-polaron-bipolaron states of polypyrrole (ppy) were analyzed by in situ Raman spectroelectrochemistry. The distinct vibrational modes presented by the polymer in different oxidation levels were assigned to specific signatures of polaron and bipolaron states. As the polymer was oxidized from the neutral state, an intermediary phase featuring vibrational bands from both the benzoid (reduced) and the quinoid (oxidized) forms were observed. This intermediary phase was correlated to the polaron state. The results were compared with previous ESR data that confirm the presence of polaron and bipolaron states in the potential region where the vibrational modes of these phases were identified.     

光激发下的C60

用电子一晶格耦合的紧束缚模型研究了光激发下的C_(60)分子。结果表明当电子由最高占据态激发到最低空态时,晶格发生弛豫,新激发态是环状双极化子,它有下述特点:键结构由基态时只有2种键长的二聚化变为有7种不同键长的层状,与基态相比,键长变化如环状极化子,赤道附近变化最大,二极处近乎不变;有2个能级进入能隙,成为自陷束缚态,它们定域在赤道附近;对称性由基态时I_h群降为D_(5d)群;预期会伴随出现非线性激子和4条核磁共振谱线。     

Structure characterization of sulfuric acid-doped poly(3-octylthiophene)

The structures of sulfuric acid-doped and water-undoped poly(3-octylthiophene) (P30T) were investigated by gel permeation chromatography (GPC), elemental analysis (EA), conductivity measurement, ultraviolet-visible-near-Infrared spectroscopy (UV-Vis-near-IR), Electron spin resonance (ESR), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). For H₂SO₄-doped P3OT, the counter ion is HSO₄ ^– and the positive charge formed on the main chain distributes only on the conjugated C-C bond and does not distribute on the S atoms. The conductivity is found to increase by 5 orders as the doping level is 0.22. After the undoping with water, C-OH groups are formed on the main chains, which results in a decrease in conjugating length and in a less order chain arrangement. The undoped P3OT film can be redoped by 98% H₂SO₄; however, the doping level is less than its original value at the same doping condition.     

导电高聚物MP-PPV的ps吸收谱研究

我们研究了在ps紫外脉冲激发下,导电高聚物MP-PPV溶液及薄膜的瞬态吸收谱。来自极化子和双极子的四个瞬态吸收带,在被稀释的MP-PPV溶液中被观察到,这些元激发的产生、迁移和衰变受不同实验条件的影响。