Polarizing energy transfer in photoluminescent materials for display applications

Abstract

Nature © Macmillan Publishers Ltd 1998 8 letters to nature NATURE | VOL 392 | 19 MARCH 1998 261and get a glimpse of the structure of the proton excited states 29,30 . The results depicted in Fig. 4 as a function of pressure further strengthen our conclusions. Upon compressing ice VIII, we find that the protons become increasingly compact, ground-state dominated and thus localized. Overstepping the phase boundary to ice VII (long dashed line), their spatial extent increases rapidly and is accompanied by a strong delocalization: that is, extended protonic states contribute significantly in addition to the ground state. Such behaviour is also characteristic immediately after crossing the phase transition to ice X (short dashed line), but there is a clear trend for protons to become strongly localized again at the highest pressure, where the underlying potential is of the single-well type.Our essential findings can be summarized as follows: (1) The sequence of the transitions is antiferroelectric ice VIII to paraelectric ice VII and finally to symmetric ice X at about 100 K; (2) the isotope effect on the antiferroelectric disordering transition (VIII → VII) is caused by translational proton tunnelling, whereas that on symmetrization (VII → X) is a qualitative zero-point motion effect; and (3) there are two 'forms' of ice X, both characterized by a unimodal proton distribution centred at the bond midpoint, the one at lower pressure being characterized by an underlying double-well proton transfer potential and a very broad proton distribution, whereas the high-pressure form has a single-well potential with a sharper proton localization. We hope that the insight we have gained from the different regimes of a 'clean' and relatively simple system, ice under controlled high pressure, will be useful in understanding quantum effects in other proton-transfer systems. Ⅺ

Polarized Luminescence from Oriented Molecular Materials

“…The most comprehensive solution to the ªbacklight problemº is a device that actively emits linearly polarized light, but this review would be incomplete without briefly discussing two related concepts, namely: l luminescent ªguestº molecules in an aligned ªhostº matrix, l circularly polarized emission. Although the penultimate approach is not particularly novel in itself, the recent introduction of polarizing excitonic energy transfer (EET) [7] into a guest/host system has made it an attractive alternative to active device concepts. The quality of alignment of a molecular material is often quantified by an orientational ªorder parameterº S. Strictly speaking, the term ªorder parameterº originates from Landau's theory of phase transitions [8] and should only be applied to anisotropic systems that are in thermodynamic equilibrium, e.g., LCs.…”

Molecular‐Scale Tracking of the Self‐Healing of Polycrystalline Monolayers at the Solid–Liquid Interface

“…We reported several p-extended donor molecules that contain a stable organic radical component, [9] and recently discovered highly conducting cation radical salts using a bis-fused TTF skeleton, 2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene (BDT-TTP, or simply ªTTPº), [10] incorporating the 2,2,5,5-tetramethyl-1-pyrrolidinyloxy (PROXYL) radical substituent 1 (Scheme 1). [11,12] However, the crystal structures of the cation radical salts based on such TTP-based donor molecules were difficult to determine because suitable crystals for crystallographic analysis had yet to be grown. Very recently, we successfully analyzed the crystal structure of small cation radical salts using a new X-ray diffractometer equipped with a confocal X-ray mirror system and a charge-coupled device (CCD) detector.…”

“…1), a stiff, rod-like, conjugated molecule peculiar in its electro-optical properties, [9±11] which renders it a prototype for organic semiconductors suitable for fabricating molecular electronic devices. [12,13] A monodisperse molecular system can physisorb at the interface between its almost-saturated solution and a highly oriented pyrolytic-graphite (HOPG) substrate, forming 2D crystals [14,15] which exhibit order that reflects the three-fold symmetry of the support. On a scale of several nanometers, the PE3 self-assembles into a polycrystalline structure (Fig.…”

Conjugated Polymers Complexed with Helical Porphyrin Oligomers Create Micron‐Sized Ordered Structures

“…addition to supramolecular assembly schemes, [3][4][5][6] a number of approaches, including metastable states enforced by liquid crystalline phases, [7][8][9] Langmuir monolayers at the air-water interface, [10] incorporation into prealigned host matrixes, [11,12] and rubbing, [13,14] have been utilized to align conjugated polymers, thus leading to some unprecedented and fascinating photophysical functions. From a supramolecular standpoint, we recently proposed a supramolecular bundling approach toward the alignment of CPs.…”