Se Hun Kim

A White-Light-Emitting Molecule: Frustrated Energy Transfer between Constituent Emitting Centers

White-light-emitting single molecules are promising materials for use in a new generation of displays and light sources because they offer the possibility of simple fabrication with perfect color reproducibility and stability. To realize white-light emission at the molecular scale, thereby eliminating the detrimental concentration- or environment-dependent energy transfer problem in conventional fluorescent or phosphorescent systems, energy transfer between a larger band-gap donor and a smaller band-gap acceptor must be fundamentally blocked. Here, we present the first example of a concentration-independent ultimate white-light-emitting molecule based on excited-state intramolecular proton transfer materials. Our molecule is composed of covalently linked blue- and orange-light-emitting moieties between which energy transfer is entirely frustrated, leading to the production of reproducible, stable white photo- and electroluminescence.

Highly efficient and stable deep-blue emitting anthracene-derived molecular glass for versatile types of non-doped OLED applications

New anthracene-based deep-blue emitting molecular glass, 9-(9-phenylcarbazole-3-yl)-10-(naphthalene-1-yl)anthracene (PCAN), which is asymmetrically functionalized with N-phenylcarbazole and naphthalene, has been designed, synthesized, and characterized. The deep-blue emitting PCAN is efficiently secured for color purity, has high glass transition temperature (Tg = 151 °C), and has excellent solubility (>100 mg mL−1 in toluene), due to its highly tilted asymmetric molecular conformation. Using processing versatility of PCAN, vacuum-deposited and solution-processed non-doped deep-blue fluorescent organic light-emitting diodes (OLEDs) were prepared, which employ PCAN as an emitter. The vacuum deposited, non-doped EL device exhibited not only the excellent luminance efficiency and external quantum efficiency (as high as 3.64 cd A−1 and 4.61%, respectively) for the saturated deep-blue CIE chromaticity coordinates of (0.151, 0.086), but also stable performance and a good device lifetime. Furthermore, the solution processed EL device also exhibited an encouraging level of performance (1.24%, 1.15 cd A−1) and deep-blue emission (0.159, 0.105).

A highly efficient wide-band-gap host material for blue electrophosphorescent light-emitting devices

We report on an efficient wide-band-gap host material for blue electrophosphorescence devices, namely, 1,2-trans-di-9-carbazolylcyclobutane (DCz). Photophysical studies show that lower-energy excimer formation between the carbazole units can be efficiently suppressed in a DCz film, thus maintaining its high triplet-state energy and inducing an exothermic energy transfer from DCz to iridium(III)bis[(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic). Electrophosphorescent devices comprising a FIrpic:DCz emitting layer exhibit a superior performance with a maximum external quantum efficiency of 9.8%, a maximum luminance efficiency of 21.5cd∕A, and a maximum power efficiency of 15.0lm∕W at 0.01mA∕cm2.

25.1: Invited Paper: White‐emitting Molecule: ‘Molecular Pixel’ from Covalently Bonded Sub‐pixels

In this presentation, we demonstrate the synthesis and properties of two-color emitting ‘molecular pixel’. Our molecule is composed of covalently linked blue- and orange-light-emitting moieties between which energy transfer is entirely frustrated, leading to the production of reproducible and stable white photo-/electroluminescence.