Noncrystallizable Molecular Glasses for Stable and Long-Lived OLED and Organic Electronics Michel F. Molaire, Molecular Glasses, Rochester, NY/USA
This presentation will be delivered at the Digital Fabrication and Digital Printing NIP30
more than printing
September 7 - 11, 2014
PRINTED ELECTRONICS MATERIALS /
PROCESSES AND SYSTEMS INTERACTIVE
Organic Light Emitting Diode Technology (OLED) is poised to challenge Light Emitting Diode (LED) and Liquid Crystal Display (LCD) in flat panel displays, flexible displays and lighting applications. OLED display has an advantage over LCD with its high response speed, wide viewing angle and high contrast in dark settings. There are however two major challenges slowing down OLED:
1. Production costs must decrease
2. Device longevity needs to improve. (1, 2, and 3)
Traditional thermal OLED production is too expensive. Solution processes for spin, roll-to-roll, slot die, or inkjet coating are required. The traditional small molecules used for thermal deposition tend to crystallize in solvents. OLED systems using polymeric materials (PLED) are being developed. Polymeric charge transport materials tend to have relatively low transport properties. Recently, there have been a lot of activities surrounding “molecular glasses” for solution smOLED processes (small molecules OLED). 4 These molecular glasses are defined as “amorphous materials in the state of thermodynamic non-equilibrium, and hence, they tend to undergo structural relaxation, exhibiting well-defined glass temperature Tg’s. However they also tend to crystallize on heating above their Tg’s, frequently exhibiting polymorphism”.5, 6 With time, equilibrium will lead to crystallization of these materials. When that happens, the performance of the device is degraded, limiting longevity. An additional problem with current small molecule OLED materials is their solubility. Either solubility is limited or requires non-green solvents.
Molecular Glasses, a division of Molaire Consulting LLC, is developing a class of truly noncrystallizable amorphous small molecule organic electronics materials with high solubility in various green solvents.7, 8 This new class of amorphous small molecule OLED materials are defined as mixtures of compatible molecules with an infinitely low crystallization rate under the most favorable conditions. They are essentially noncrystallizable with large entropy of mixing values amenable to compatibility with a wide range of materials at very high concentration.
This presentation will report on the design, synthesis, and characterization of noncrystallizable electron-transporting, hole-transporting, bipolar charge-transporting and luminescent small molecule materials. The concept behind this class of compounds and the reasons for their efficacy will be discussed.
Keywords: Noncrystallizable small molecule materials, noncrystallizable electron-transporting small molecule materials, noncrystallizable hole-transporting small molecule materials, noncrystallizable bipolar charge-transporting small molecule materials, noncrystallizable luminescent small molecule materials, smOLED materials, green solvent solubility, large entropy of mixing.
1. Jong Hyuk Lee at Al, Materials Issues in AMOLED, www.intechopen.com
2. Yung-Ting Chang et al, ACS Appl. Mater. & Interfaces, 2013, 5, 01614-10622
3. Tomoyuki Shirasaki, SID 04 Digest
4. Peter Strohriegl, Juozas V. Grazulevicius, Adv. Mater. 2002, 14, No 20, October 16;
5. Hari Singh Nalwa, Advanced Functional Molecules and Polymers, Volume 3, CRC Press, 2001 - Technology & Engineering
6. Yashuhiko Shirota and Hiroshi Kageyama, Chem. Rev.2007, 107, 953-1010
7. M. F. Molaire, 5 pending patents
8. Michel Molaire, Roger Johnson, Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 27, 2569-2592 (1989)