For the Next Stage of Organic Optoelectronic Devices


Focusing on properties and concepts specific to organic materials, we are trying to clarify the physics in organic semiconductors, improve their performances, and create novel devices.

Since organic semiconductors are composed of molecules weakly bound, they have significantly different properties and concepts from those of inorganic semiconductors: for example, molecular orientation, intermolecular interaction, and wavelength selectivity. We are investigating such properties of various kinds of materials and solid films used for organic semiconductor devices. By extracting higher-order concepts with a high generality from datailed analysis, we are trying to establish the fundamentals in organic semiconductor devices from the viewpoint of "Molecular physics". Furthermore, applying the advantages of the properties to actual devices, we are also targeting significant improvement of device performance and creation of novel organic optoelectronic devices.

Molecular physics, Organic semiconductor devices (OLEDs, OPVs, etc), Molecular orientation, Intermolecular interactions, Organic photophysics
[Related techniques]
Spectroscopic ellipsometry, Quantum calculation, Optical simulation, Fabrication and evaluation of organic devices


We have started research activities in Department of Organic Device Engineering, Yamagata University since December, 2009.


  • Apr. 1, 2013 Schedule of talk in a conference:
    The 6th International Conference on Spectroscopic Ellipsometry (ICSE-VI)
    (Kyoto, Japan) May. 26-31, 2013
    Invited 06:
    Optical anisotropy and molecular orientation in amorphous organic semiconductor films
    Daisuke Yokoyama

  • Apr. 1, 2013 Research summary:
    As a summary of our recent works, the abstract in A-COE2012 was uploaded.
    A-COE2012 Abstract

  • Apr. 1, 2013 New members:
    A new student joined our lab.

  • Apr. 1, 2013 Tenure-track period finished:
    The tenure-track period finished, and Yokoyama officially joined the faculty as an associate professor.

  • Dec. 23, 2012 International conference in our campus finished successfully:
    A-COE2012 was held in our campus on Dec. 19-21 and finished successfully. We sincerely thank all speakers and participants.
    A-COE2012 Photos

  • Dec. 7, 2012 Journal cover selected:
    The research paper on refractive index control of organic semiconductors was selected as the back cover of Vol. 24, Issue 47 (2012) of Advanced Materials. Website [PDF 2.5MB]

  • Nov. 14, 2012 International conference in Yonezawa:
    A-COE2012 (The 4th Asian Conference on Organic Electronics) will be held in our campus on Dec. 19-21.
    A-COE2012 Website

  • Oct. 24, 2012 Paper accepted and published:
    A research paper on highly efficient OPVs with CT absroption and molecular orientation in the co-deposited layers was accepted and published by Energy Environ. Sci.
    "Highly efficient organic p-i-n photovoltaic cells based on tetraphenyldibenzoperiflanthene and fullerene C70"
    Zhongqiang Wang, Daisuke Yokoyama, Xiao-Feng Wang, Ziruo Hong, Yang Yang, Junji Kido, Energy Environ. Sci. (in press)

  • Oct. 2, 2012 New members:
    Two students joined our lab.

  • Sep. 18, 2012 Paper published:
    A research paper on wide-range refractive index control of organic semiconductors was published in Adv. Mater.
    "Wide-range refractive index control of organic semiconductor films toward advanced optical design of organic optoelectronic devices"
    D. Yokoyama, K. Nakayama, T. Otani, J. Kido, Adv. Mater. (in press)

  • Aug. 27, 2012 Seminar talk in University of Florida:
    A seminar in University of Florida was held under the support by Prof. Franky So. The details about molecular orientation analysis and refractive index control were shown.

  • Aug. 8, 2012 Paper accepted:
    A research paper on a squaraine dye in photovoltaic cells was accepted by Appl. Phys. Lett.
    "Optical and electrical properties of a squaraine dye in photovoltaic cells"
    G. Chen, D. Yokoyama, H. Sasabe, Z. Hong, Y. Yang, J. Kido, Appl. Phys. Lett. (in press)

  • Aug. 3, 2012 Paper accepted:
    A research paper on wide-range refractive index control of organic semiconductors was accepted by Adv. Mater. (The patent was also filed.) This is a fundamental research on optical properties of organic semiconductor films and devices, which can apply to all advanced organic optoelectronic devices such as OLEDs, OPVs, organic lasers, and so on.

  • Apr. 23, 2012 Research summary:
    Our studies are summarized in these research digest and review paper.
    Research digest [PDF 1.3MB]
    Invited review paper [PDF 4.0MB]

  • Apr. 17, 2012 Schedule of talk in conferences:
    SPIE Optics+Photonics (San Diego, US) Aug. 12, 2012
    [Invited] Functional group orientation in amorphous films of OLED materials
    IMID 2012 (Daegu, Republic of Korea) Aug. 28-31, 2012
    [Invited] TBD

  • Feb. 9, 2012 Schedule of talk in a conference:
    2012 MRS Spring Meeting "Symposium J" (San Francisco, US) Apr. 10 (Tue), 2012
    J5.2 [Invited] Molecular orientation in OLEDs
    Daisuke Yokoyama

  • Dec. 8, 2011 Selected as one of the "Most read articles":
    The review paper published in J. Mater. Chem. was selected as the 3rd in "Most read articles" of the journal (on Dec. 8).

  • Nov. 1, 2011 Introduction by OLED website:
    The review paper published in J. Mater. Chem. was introduced by the website of "OLED-Info", which shows the latest information on OLED technologies.

  • Oct. 27, 2011 Review paper published:
    An invited review paper (Feature Article) on molecular orientation in OLEDs was published by J. Mater. Chem. We hope that you will kindly read this paper and have an interest in this study. [PDF 4.0MB]

  • Oct. 8, 2011 Paper accepted:
    A research paper on OPVs with horizontally oriented amorphous materials was accepted by Sol. Energy Mater. Sol. Cells.

  • Oct. 8, 2011 Update of some English pages! (partially)

  • Sep. 8, 2011 Schedule of talk in a conference:
    IMID 2011 (Seoul, Korea) Oct. 12 (Wed), 2011
    20-3: [Invited] Molecular orientation in organic light-emitting diodes
    Daisuke Yokoyama

  • Aug. 28, 2011 Paper accepted:
    A research paper on high-efficiency fluorescent OLEDs with delaeyd fluorescetnce and dipole orientation was accepted by Appl. Phys. Lett.