Orientation Control of Linear‐Shaped Molecules in Vacuum‐Deposited Organic Amorphous Films and Its Effect on Carrier Mobilities

Yokoyama, Daisuke; Setoguchi, Yousuke; Sakaguchi, Akio; Suzuki, Michio; Adachi, Chihaya

doi:10.1002/adfm.200901684

Cited by 157 publications

(234 citation statements)

References 19 publications

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“…Thus, the decrease in absorbance reflects the randomization of molecular orientation. 17) In contrast to the considerable changes in the absorbances of the vacuum-deposited films, those of the spincoated films were nearly unchanged after annealing. This result directly demonstrates that the molecular orientations in the as-prepared spin-coated films are nearly random similarly to those in the annealed spin-coated films.…”

mentioning

confidence: 97%

Simple model-free estimation of orientation order parameters of vacuum-deposited and spin-coated amorphous films used in organic light-emitting diodes

Sakai

Shibata

Yokoyama

2015

Appl. Phys. Express

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Molecular orientation in organic light-emitting diodes (OLEDs) is now regarded as an important factor that affects device efficiency. However, methods to quantitatively estimate the degree of molecular orientation in OLEDs are currently limited, and they require constructing a model of an optical structure. Here, we propose a simple model-free method to estimate the orientation order parameters (S) of molecules in amorphous OLED films from their absorption spectra using the randomization of molecular orientation induced by heating. This method is used to quantitatively estimate the S values of vacuum-deposited and spin-coated films and clearly demonstrate the random orientation in the latter.

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confidence: 97%

Simple model-free estimation of orientation order parameters of vacuum-deposited and spin-coated amorphous films used in organic light-emitting diodes

Sakai

Shibata

Yokoyama

2015

Appl. Phys. Express

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“…This result is very promising for using these materials for phosphorescent OLEDs [10] and as donor materials for organic solar cells. [29][30][31][32] Experimental Section X-ray data for Ir1a:C 85 H 95 F 8 .Phasenomenclature: Cr = crystal, SmA = smectic Am esophase, Iso = isotropic liquid. .C CDC 1418808 contains the supplementary crystallographic data for this paper.T hese data are providedf ree of charge by The Cambridge Crystallographic Data Centre.…”

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confidence: 99%

Blue and Green Phosphorescent Liquid‐Crystalline Iridium Complexes with High Hole Mobility

Wang

Cabry

Xiao

et al. 2015

Chemistry A European J

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Blue- and green-emitting cyclometalated liquid-crystalline iridium complexes are realized by using a modular strategy based on strongly mesogenic groups attached to an acetylacetonate ancillary ligand. The cyclometalated ligand dictates the photophysical properties of the materials, which are identical to those of the parent complexes. High hole mobilities, up to 0.004 cm(2) V(-1) s(-1), were achieved after thermal annealing, while amorphous materials show hole mobilities of only approximately 10(-7) -10(-6) cm(2) V(-1) s(-1), similar to simple iridium complexes. The design strategy allows the facile preparation of phosphorescent liquid-crystalline complexes with fine-tuned photophysical properties.

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“…There has been considerable recent interest in controlling molecular orientation in organic semiconducting glasses (1)(2)(3)(4)(5)(6)(7). Whereas one might expect all glasses to be isotropic because of their structural disorder, Yokoyama et al and other groups have shown that molecular orientation in vapor-deposited glasses can be quite anisotropic (3,4,8,9) and depend upon deposition conditions (3).…”

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confidence: 99%

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

Dalal

Walters

Lyubimov

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

197

351

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Physical vapor deposition is commonly used to prepare organic glasses that serve as the active layers in light-emitting diodes, photovoltaics, and other devices. Recent work has shown that orienting the molecules in such organic semiconductors can significantly enhance device performance. We apply a high-throughput characterization scheme to investigate the effect of the substrate temperature (T substrate ) on glasses of three organic molecules used as semiconductors. The optical and material properties are evaluated with spectroscopic ellipsometry. We find that molecular orientation in these glasses is continuously tunable and controlled by T substrate /T g , where T g is the glass transition temperature. All three molecules can produce highly anisotropic glasses; the dependence of molecular orientation upon substrate temperature is remarkably similar and nearly independent of molecular length. All three compounds form "stable glasses" with high density and thermal stability, and have properties similar to stable glasses prepared from model glass formers. Simulations reproduce the experimental trends and explain molecular orientation in the deposited glasses in terms of the surface properties of the equilibrium liquid. By showing that organic semiconductors form stable glasses, these results provide an avenue for systematic performance optimization of active layers in organic electronics.glasses | organic semiconductors | molecular orientation | physical vapor deposition | high-throughput characterization

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Orientation Control of Linear‐Shaped Molecules in Vacuum‐Deposited Organic Amorphous Films and Its Effect on Carrier Mobilities

Cited by 157 publications

References 19 publications

Simple model-free estimation of orientation order parameters of vacuum-deposited and spin-coated amorphous films used in organic light-emitting diodes

Simple model-free estimation of orientation order parameters of vacuum-deposited and spin-coated amorphous films used in organic light-emitting diodes

Blue and Green Phosphorescent Liquid‐Crystalline Iridium Complexes with High Hole Mobility

Tunable molecular orientation and elevated thermal stability of vapor-deposited organic semiconductors

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