Synthesis,Structure, Photophysical Properties,and Photostability of Benzodipyrenes

This work explores the syntheses, structures, photophysical properties, and photostability of benzodipyrenes (BDPs). BDPs were synthesized through an InCl₃-AgNTf₂-catalyzed, four-fold alkyne benzannulation reaction. The structures of BDP 4 a and its corresponding endoperoxide product were unambiguously confirmed by X-ray crystallography. The BDPs reported here can also be recognized as peri- and cata-benzannulated pentacenes with a non-functionalized central ring. Unlike the previous reported pentacene-based polycyclic aromatic hydrocarbons, the absorbances of the BDPs were blueshifted by ca. 40 nm relative to pentacene, even after extension of π-conjugation. The newly synthesized BDP products exhibit relatively good stability with half-lives as high as 4612 min in THF.     

The pentacene films on the glass/ITO surface: structure and optical properties

Abstract

The structure, morphology and optical transmittance spectra of pentacene films on the (glass/ITO) surface were studied. The films were grown by two methods - the thermal vacuum deposition (TVD) and pulsed laser deposition (PLD). The electron diffraction pattern from thermally deposited pentacene films confirms their polycrystalline structure while the diffraction pattern of PLD-coated layers has a diffusion character. The results obtained showed that layers deposited by the TVD method has an optical spectrum that is characteristic for the pentacene film in contrary to the layers deposited by the PLD method. It is found a sensitivity of the optical transmittance of pentacene films to the ammonia action, which may be used for development the optical gas sensor.     

Characteristics of pentacene organic thin film transistor with top gate and bottom contact

High performance pentacene organic thin film transistors (OTFT) were designed and fabricated using SiO₂ deposited by electron beam evaporation as gate dielectric material. Pentacene thin films were prepared on glass substrate with S--D electrode pattern made from ITO by means of thermal evaporation through self-organized process. The threshold voltage V_TH was --2.75± 0.1V in 0---50V range, and that subthreshold slopes were 0.42± 0.05V/dec. The field-effect mobility (μ_EF) of OTFT device increased with the increase of V_DS, but the μ_EF of OTFT device increased and then decreased with increased V_GS when V_DS was kept constant. When V_DS was --50V, on/off current ratio was 0.48× 10⁵ and subthreshold slope was 0.44V/dec. The μ_EF was 1.10cm²/(V.s), threshold voltage was --2.71V for the OTFT device.     

并五苯同质异相体中分子间势能与能带计算

采用Born-Mayer-Haggins对势模型，分析了并五苯分子间势能及其相互作用. 用紧束缚模型计算了两种并五苯同质异相体结构的能带宽度. 计算带宽随温度升高减小8%—14%. 关键词： 并五苯 同质异相体 分子间势能 能带计算     

Enhanced mobility and environmental stability in all organic field‐effect transistors: The role of high dipole moment solvent

Low‐operating voltage, high mobility, and stable organic field‐effect transistors (OFETs) using polymeric dielectrics such as pristine poly(4‐vinyl phenol) (PVP) and poly(methyl methacrylate) (PMMA), dissolved in solvents of high dipole moment, have been achieved. High dipole moment solvents such as propylene carbonate and dimethyl sulfoxide used for dissolving the polymer dielectric enhance the charge carrier mobilities by three orders of magnitude in pentacene OFETs compared with low dipole moment solvents. Fast switching circuits with patterned gate PVP‐based pentacene OFETs demonstrated a switching frequency of 75 kHz at input voltages of |5 V|. The frequency response of the OFETs is attributed to a high degree of dipolar‐order in dielectric films obtained from high‐polarity solvents and the resulting energetically ordered landscape for transport. Remarkably, these pentacene‐based OFETs exhibited high stability under bias stress and in air with negligible shifts in the threshold voltage. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1533–1542     

Large Optical Nonlinearity Induced by Singlet Fission in Pentacene Films

By creating two triplet excitons from one photo‐excited singlet exciton, singlet fission in organic semiconductors has drawn tremendous attention for its potential applications in boosting the efficiency of solar conversion. Here, we show that this carrier‐multiplication effect can also be used to dramatically improve the nonlinear optical response in organic materials. We have observed large optical nonlinearity with a magnitude of χ⁽³⁾ up to 10^?9 esu in pentacene films, which is further shown to be a result of singlet fission by monitoring the temporal dynamics. The potential application of such efficient nonlinear optical response has been demonstrated with a singlet‐fission‐induced polarization rotation.     

Axial coordination of pyridyl-containing pentacenes to porphyrins

A pair of pentacenes that are functionalized in the 6-position with either a 3- or 4-pyridyl group via a triazole linker have been used to form complexes with a tetra(aryl)ruthenium(II) porphyrin through axial coordination. The pentacene–porphyrin dyads 5 and 6 have been structurally characterized through a combination of spectroscopic techniques. UV–vis spectroscopy shows that the absorption profiles of the two chromophores, the porphyrin and the pentacene, are complementary, providing absorptions throughout the UV and visible regions. While the dyads are reasonably stable in the solid state under ambient conditions they are, unfortunately, only stable in solution for hours when exposed to light and air.     

Impact of molecular tilt angle on the absorption spectra of pentacene:perfluoropentacene blends

We investigate the relation between the optical properties and the average molecular tilt angle for blends of pentacene and perfluoropentacene, which can be considered as a prototypical donor–acceptor complex. Combining near‐edge X‐ray absorption fine‐structure spectroscopy and optical spectroscopy we study thin films of these compounds prepared at three different substrate temperatures T_sub. For T_sub =180 K we observe a larger average tilt angle than for blends prepared at higher substrate temperatures. This orientational change has significant impact on the uniaxial anisotropic optical properties of the mixed films which we measure post growth as well as in real‐time during growth. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

对以并五苯和酞菁铜为不同有源层的有机薄膜晶体管特性研究

通过扫描电镜和X射线衍射对SiO₂衬底上生长并五苯和酞菁铜薄膜的表面形貌进行表征,并得到在SiO₂衬底上生长的并五苯薄膜是以岛状结构生长,其大小约为100nm,且薄膜有较好的结晶取向,呈多晶态存在. 酞菁铜薄膜则没有表现出明显的生长机理,其呈非晶态存在. 还对通过掩膜的方法制作得以酞菁铜和并五苯为有源层的顶栅极有机薄膜晶体管的特性进行了研究. 有源层的厚度为40nm,绝缘层SiO₂的厚度为250nm,器件的沟道宽长比(W/关键词： 有机薄膜晶体管 并五苯薄膜 酞菁铜薄膜 μ_EF)')" href="#">场效应迁移率(μ_EF)