Korea Advanced Institute of Science and Technology · Engineering
Professor O-Pil Kwon's research lab specializes in the design, synthesis, and crystal engineering of organic nonlinear optical (NLO) materials, with a focus on developing highly efficient electro-optic and terahertz-active crystals. The lab pioneers novel chromophore architectures—particularly acentric ionic systems based on quinolinium, benzothiazolium, and stilbazolium cores—engineered for strong macroscopic optical nonlinearity and enhanced molecular hyperpolarizability. Their work emphasizes crystal growth from solution and melt, structure-property relationships, and applications in terahertz wave generation and photonic devices.
Figures are computed from collected data and may differ slightly.
Abstract We investigate a configurationally locked polyene (CLP) crystal 2‐(3‐(4‐hydroxystyryl)‐5,5‐dimethylcyclohex‐2‐enylidene)malononitrile (OH1) containing a phenolic electron donor, which also acts as a hydrogen bond donor. The OH1 crystals with orthorhombic space group Pna2 1 (point group mm2) exhibit large second‐order nonlinear optical figures of merit, high thermal stability and very favorable crystal growth characteristics. Higher solubility in methanol and a larger temperature differe
Abstract A novel highly efficient ionic electro‐optic quinolinium single crystals for THz wave applications is reported. Acentric quinolinium derivatives, HMQ‐T (2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 4‐methylbenzenesulfonate) and HMQ‐MBS (2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 4‐methoxybenzenesulfonate) exhibit high order parameters cos 3 θ p = 0.92 and cos 3 θ p = 1.0, respectively, as well as a large macroscopic optical nonlinearity, which is in the range of the benchmar
A series of nonlinear optical chromophores based on configurationally locked polyene are synthesized, and the single crystal growth from the melt are investigated. The chromophores consist of a π-conjugated hexatriene bridge between the dialkylamino or methoxy electron donors and the dicyanomethylidene electron acceptor. The physical and nonlinear optical properties and the single crystal X-ray structures of these chromophores are characterized. Specifically, the chromophore 2-{3-[2-(4-dimethyla
We have developed a new cation core structure, N-benzyl stilbazolium nonlinear optical chromophore with a non-polar benzyl group to achieve acentric molecular ordering in the crystalline state. New N-benzyl stilbazolium crystal, BP3 (N,N-dimethylamino-N′-2,5-dimethylbenzyl-stilbazolium p-toluenesulfonate), exhibits an acentric crystal structure with the monoclinic P21 phase with a large macroscopic optical nonlinearity of 540 times the powder second harmonic generation efficiency of urea at the
Highly efficient nonlinear optical organic crystals are very attractive for various photonic applications including terahertz (THz) wave generation. Up to now, only two classes of ionic crystals based on either pyridinium or quinolinium with extremely large macroscopic optical nonlinearity have been developed. This study reports on a new class of organic nonlinear optical crystals introducing electron-accepting benzothiazolium, which exhibit higher electron-withdrawing strength than pyridinium a
Organic electrooptic crystals based on a new acentric core structure 2-(4-hydroxystyryl)-1-methylquinolinium provide optimal molecular packing for maximizing the electrooptic response. They allow intense broadband terahertz generation with over 30 times higher terahertz generation efficiency compared to the widely used inorganic ZnTe. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-orga
New pyrrolic viscosity sensors exhibit one order of magnitude higher fluorescence contrast compared to that of the conventional phenolic analogues due to the viscosity-sensitive rotation of the asymmetric pyrrole group and successfully demonstrate mapping of intracellular viscosity by fluorescence lifetime imaging microscopy.
This study investigates the performance of single-crystalline nanomaterials of wide-band gap naphthalene diimide (NDI) derivatives with methylene-bridged aromatic side chains. Such materials are found to be easily used as high-performance, visible-blind near-UV light detectors. NDI single-crystalline nanoribbons are assembled using a simple solution-based process (without solvent-inclusion problems), which is then applied to organic phototransistors (OPTs). Such OPTs exhibit excellent n-channel
For terahertz (THz) wave generators based on organic electrooptic crystals, their intrinsic phonon modes are playing an essential role in THz generation characteristics. Here, this study proposes an effective design strategy for THz phonon mode engineering of organic electrooptic salt crystals for efficient optical‐to‐THz frequency conversion. To reduce phonon‐mode intensity, strongly electronegative trifluoromethyl group acting as strong hydrogen‐bond acceptor is incorporated into molecular ani
A series of new organic nonlinear optical nitrophenylhydrazone crystals based on pyrrole with various substituents (X: -H, -CH3, -CF3) on the hydrazone group (–CX═N–NH–) has been synthesized and their polymorphs have been investigated. The chromophore 2-((2-(4-nitrophenyl)hydrazono)methyl)-1H-pyrrole (HNPH) exhibits two polymorphs with large macroscopic nonlinearity, with a powder second harmonic generation activity of 420 times and 210 times that of urea at 1.9 μm for the anisotropic polar HNPH
A design strategy is proposed for electron-transporting materials (ETMs) with homochiral asymmetric-shaped groups for highly efficient non-fullerene perovskite solar cells (PSCs). The electron transporting N,N'-bis[(R)-1-phenylethyl]naphthalene-1,4,5,8-tetracarboxylic diimide (NDI-PhE) consists of two asymmetric-shaped chiral (R)-1-phenylethyl (PhE) groups that act as solubilizing groups by reducing molecular symmetry and increasing the free volume. NDI-PhE exhibits excellent film-forming abilit
Configurationally locked polyene crystals grown in the absence and in the presence of their tailor-made auxiliaries, which are slightly modified substrate molecules, were investigated. The effects of the tailor-made auxiliaries on the crystal characteristics were investigated by X-ray crystal structure analysis and nonlinear optical and photoluminescent measurements. The substrate crystals of 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2) and 2-{3-[2-
Abstract This study presents newly developed yellow‐colored organic electro‐optic crystals to provide high terahertz (THz) wave generation efficiency. Compared with currently existing red‐ or orange‐colored electro‐optic crystals, which are used for most benchmark organic THz sources, yellow‐colored crystals have additional superior advantages for THz wave generation, e.g., higher transparency in the visible wavelength range with accompanying different phase‐matching possibilities. The new yello
We report on the design of the nonlinear optical organic phenolic polyene crystals for tailoring their physical properties to achieve optimized crystals for applications. New phenolic OH2 (2-(3-(4-hydroxystyryl)-5-methylcyclohex-2-enylidene)malononitrile) molecules keep the main supramolecular interaction sites and the high hyperpolarizability of the previously studied state-of-the-art OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile) and OH3 (2-(3-(4-hydroxystyryl)cycl
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