Epitaxial Growth of Thiophene/p-Phenylene Co-oligomers for Highly Polarized Light-Emitting Crystals

Yanagi, Hisao; Morikawa, Takayuki; Hotta, Shu; Yase, Kiyoshi

doi:10.1002/1521-4095(200103)13:5<313::aid-adma313>3.0.co;2-0

Cited by 83 publications

(26 citation statements)

References 9 publications

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“…Recent progress demonstrated that this is analogous to the case of a newly emerging class of semiconducting molecular crystals, thiophene/phenylene co-oligomers. 13 These materials were developed by Hotta and co-workers 14 and are characterized by a variety of extensions of conjugation along the backbone. The conjugation extension can be tuned by changing the total number of thiophenes and phenylenes and their arrangement in the molecules.…”

supporting

confidence: 82%

Emission gain narrowing from single crystals of a thiophene/phenylene co-oligomer

Nagawa

Hibino

Hotta

et al. 2002

Applied Physics Letters

126

116

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Emission gain narrowing has been observed for single crystals of a thiophene/phenylene co-oligomer. The hexagon flake crystals were placed on a quartz substrate with the crystals' face in close contact with the substrate plane. These crystals were irradiated with a N 2 laser with a 337.1 nm wavelength at a repetition rate 10 Hz that tuned its intensity to 100-1150 J/cm 2 . The emission gain narrowing takes place at 21490 ͑465.4 nm͒ and 20220 cm Ϫ1 ͑494.5 nm͒ with increased intensities, with their half width at half maxima reaching ϳ50 cm Ϫ1 . On the basis of the nonlinear relationship between the emission peak intensities and the laser light intensity, the gain narrowing has been attributed to the amplified spontaneous emission. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1435797͔ Conjugated semiconducting polymers and oligomers are currently attracting great attention as potentially useful materials for optoelectronic devices such as thin-film transistors and light-emitting diodes. 1 Solid-state lasing and amplified spontaneous emission ͑ASE͒ have been observed in these materials. 2 Since excitation through photopumping is a facile way to attain lasing and ASE, this method has long been used. [3][4][5] The earliest examples can be found for anthracene molecules embedded in host matrices of, e.g., fluorene. 6 Later this approach was more widely applied to dye-doped systems and polymer thin films. 7 Very recently solid-state injection lasing was achieved using a tetracene single crystal, vouching for the high practicality of organic semiconductors. 8 In view of current injection, crystals of high quality are more advantageous than any other systems that involve defects which may well act as carrier traps. Reported observation of lasing or ASE of the crystals, however, remains scarce even in the case of photopumping. This is partly because the photoluminescent efficiency of chromophores is decreased by higher concentrations, 9 even though their efficiency is high at dilution. Yet a typical examples for the ASE haves been verified by Fichou et al. 10 and by Horowitz et al. 11 using single crystals of octithiophene and sexithiophene, respectively.Yanagi and Morikawa 12 showed that self-waveguided emission takes place along the crystals' long axis of needleshaped crystals of p-sexiphenyl that are epitaxially grown on top of a single crystal substrate of potassium chloride. The molecular axes of p-sexiphenyl align perpendicular to the crystals' needle axis so that the propagation of the polarized emission can be enhanced with the transverse electric mode along that needle. The uniaxially aligned transition dipoles in the p-sexiphenyl crystals are responsible for the selfwaveguided emission. Recent progress demonstrated that this is analogous to the case of a newly emerging class of semiconducting molecular crystals, thiophene/phenylene co-oligomers. 13 These materials were developed by Hotta and co-workers 14 and are characterized by a variety of extensions of conjugation along the backbone. The conjugation ...

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supporting

confidence: 82%

Emission gain narrowing from single crystals of a thiophene/phenylene co-oligomer

Nagawa

Hibino

Hotta

et al. 2002

Applied Physics Letters

126

116

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“…[3,4] The family of these oligomer materials is characterized by the well-defined molecular axes and exhibits various interesting electric transport and light emission features on the basis of the disposition of their axes in thin films and crystals. [5][6][7][8] In particular, the thiophene/phenylene co-oligomers have a variety of extension of π-conjugation along the backbone. The conjugation extension can be tuned by changing the total number of the thiophenes and phenylenes and their mutual arrangement in the molecules.…”

mentioning

confidence: 99%

Improved Crystal‐Growth and Emission Gain‐Narrowing of Thiophene/Phenylene Co‐Oligomers

Ichikawa¹,

et al. 2003

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Large plate‐like single crystals of several millimeters to ∼ 1 cm in size of organic semiconducting materials are prepared via an improved crystal‐growth technique. The crystals (see Figure) exhibit self‐waveguided amplified spontaneous emission with a relatively small threshold resulting from the excellent optical properties of the crystals, such as high transparency and low light scattering.

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“…Guided by this simple molecular design principle, these oligomers are predestinated to explore structure-property relationship for organic semiconductors. These phenyl-thiophene co-oligomers have attracted attention due to their potential as active components in OLEDs, organic diode lasers, and p-type semiconductors in OFETs [80,[234][235][236][237][238][239][240][241][242][243]. Noteworthy features are electroluminescence [237], and emission gain narrowing like spectrally narrowed emission (SNE) [244][245][246], and amplified spontaneous emission (ASE) caused by self-waveguide effects [247][248][249], and even mirrorless lasing [250,251].…”

Section: Discussionmentioning

confidence: 99%

“…Similar fiberlike structures have been obtained by Yanagi et al [80,237,241] after vapour deposition of PPTTPP onto a cleaved ionic KCl (1 0 0) surface at elevated substrate temperatures. The green fluorescent fiberlike crystals epitaxially grow along the orthogonal 1 1 0 directions of the KCl substrate.…”

Section: Ppttppmentioning

confidence: 99%

“…XRD-patterns suggest that the crystalline fibers have either their (1 0 0) or (0 1 0) faces, i.e. bc-plane or ac-plane in contact with the KCl surface [241] as assumed similar for the case of PPTTPP on muscovite mica. PPTTPP has been deposited on a muscovite mica substrate for different substrate temperatures, namely a temperature range from room temperature to 460 K is covered.…”

Section: Ppttppmentioning

confidence: 99%

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Organic Molecular Nanotechnology

Schiek

Balzer

Al‐Shamery

et al. 2008

Small

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Zur Homepage der Dissertation AbstractFormation of needle-like crystals from inorganic as well as from organic semiconductors such as para-phenylenes, α-thiophenes and phenyl-thiophene co-oligomers on dielectric surfaces has attracted increasing interest within the last years. The para-hexaphenylene has proven to be a versatile building block for generating long, parallely aligned organic nanofibers by a self-assembly process on a muscovite mica substrate via sublimation in high vacuum. These nanofibers possess outstanding optical properties like strong, polarised blue fluorescence in high quantum yields after unpolarised excitation with UV light, waveguiding and lasing features. Furthermore, they are chemically and thermically stable and can be easily detached from the growth substrate to serve as key elements in next generation optoelectronic and nanophotonic devices. Owing to their typical height and width on a nanometer scale and length up to one millimeter, the fibers bridge the gap between microscopic and macroscopic dimensions. The morphology of the nanofibers (length, height, width, aspect ratio, bending into rings) is susceptable to process parameters and pretreatment of the substrate. But chemically functionalisation of the molecular building block as key step of this thesis widens the scope of possibilities: Nanoaggregates with tailored morphology and optical properties are generated from designed functionalised molecular building blocks. Functional groups have been implemented at the 1,4´´´-para-positions of p-quaterphenylenes using a non-trivial Suzuki cross-coupling strategy. Symmetrically as well as non-symmetrically functionalised oligomers have been achieved in excellent yields and high purity. Additionally, the synthesis of phenyl-thiophene cooligomers and their acceptability for the nanofiber growth on muscovite mica via organic molecule deposition in high vacuum are presented. The fluorescence peak emission frequency of the nanostructures from the substituted p-quaterphenylenes shifts within the blue depending on the functionalisation. While dimensions are still influenced by the growth parameters, the overall shape (i.e. cross-section) of the aggregates alters significantly with the functional group. Even new properties like nonlinear optical activity are accessible. Due to intrinsic nonzero hyperpolarisability of push-pull functionalised oligomers, the respective nanofibers act as frequency doublers and emit strong second harmonic light after excitation with near infrared femtosecond laser pulses. Note that this design approach is possible while conserving the concept of highly crystalline nanofibers. Thus, a new route of bottom-up nanotechnology is presented starting from organic molecular synthesis towards generating of tailormade organic nanofibers opening new prospects for future nanotechnology. 3 ZusammenfassungDie Bildung von nadelförmigen Kristallen aus anorganischen und organischen Halbleitermolekülen wie zum Beispiel para-Phenylenen, α-Thiophenen und Phenylthiophen Co-oligomeren fa...

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Epitaxial Growth of Thiophene/p-Phenylene Co-oligomers for Highly Polarized Light-Emitting Crystals

Cited by 83 publications

References 9 publications

Emission gain narrowing from single crystals of a thiophene/phenylene co-oligomer

Emission gain narrowing from single crystals of a thiophene/phenylene co-oligomer

Improved Crystal‐Growth and Emission Gain‐Narrowing of Thiophene/Phenylene Co‐Oligomers

Organic Molecular Nanotechnology

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