Deuterated semi-conducting organic compounds used for opto-electronic devices

#The present invention relates to new semiconducting organic compounds and/or polymers for use in optoelectronic devices that contain completely or partially deuterated conjugated backbones, which can promote luminescence and thermal stability of the materials. More particularly, the present invention relates to the effective modification of the molecular structure of known luminescent materials with conjugated backbones containing hydrogen atoms by replacing one or more of the hydrogen atoms with deuterium atoms. The resulting deuterated material is significantly altered and has greatly improved performance over known luminescent light-emitting materials.

#Organic semiconductors have the benefit of low cost processing, easy control of properties by changing chemical structures, and attractive electronic properties. These materials are usually composed of conjugated chromophores linked by saturated or unsaturated linkage units. Many interesting applications have been explored in recent years, such as organic light-emitting devices [C. W. Tang, S. A. Van Slyke, Appl. Phys. Lett., 1987, 51(12), 913; J. H. Burroughes; D. D. C. Bradley; A. R. Brown; R. N. Marks; K. Mackay; R. H. Friend; P. L. Burn and A. B. Holmes, Nature 1990, 347, 539. R. H. Friend; R. W. Gymer; A. B. Holmes; J. H. Burroughes; R. N. Marks; C. Taliani; D. D. C. Bradley; D. A. Dossantos; J. L. Bredas; M. Logdlund and W. R. Salaneck, Nature 1999, 397, 121.], organic lasers [F. Hide; M. A. Diaz-Garcia; B. J. Schwartz and A. J. Heeger, Acc. Chem. Res. 1997, 30, 430.], organic thin-film transistors [F. Gamier, R. Hajlaoui, A. Yassar, P. Srivastava, Science, 1994, 265, 1684], and organic photodiodes.

#One application of organic semiconductors is as an active flat-panel display or organic light-emitting device (OLED). Such devices offer many unique features, including a low cost, full color, active display with the possibility of a thinner, lighter, larger and more flexible display module, with wider viewing angles (>160°), compared to conventional flat-panel display devices. All these features imply a strong competitive alternative to replace present LCD displays. Such devices consist of one or several semiconducting organic layer(s) sandwiched between two electrodes. When an electric field is applied, electrons are injected by the cathode into the lowest un-occupied molecular orbital (LUMO) of the adjacent molecules, and holes are injected by the anode into the highest occupied molecular orbital (HOMO). As a result of recombination of electrons and holes, an excited state, called singlet exciton, is formed which returns back to the ground state upon emission of light corresponding to the energy band gap of the emissive material. The selection of emissive materials not only can influence the emission color, but also the light emission efficiency (photons per injected electron) and the light emission brightness and lifetime. In practical display applications, color purity, light-emission efficiency, brightness and lifetime are important parameters.

#FIG. 1 is a cross-section illustration of a typical single layer light emitting device.

#FIG. 2 is a cross-section illustration of a typical triple layer light emitting device.

#FIG. 3 is a graph of the UV spectrum of the sulfonium polymer precursor and the converted conjugated polymer deuterated PPV (D-PPV), showing the band gap changes from 3.42 eV to 2.45 eV.

#Virtually all organic luminescent materials now marketed contain hydrogen atoms, each of which has a molecular mass of one. According to the present invention one or more of the hydrogen atoms on a conjugated chromophore or a conjugated polymer are deuterated. The molecular mass becomes higher, and the optical and electronic properties of the conjugated luminescent material are altered and improved. The deuterated organic semiconductor has improved performance, for instance, higher fluorescence yield and more stability than its non-deuterated analogue.

#There are several deuterated structures or structural combinations that may be used to form conjugated chromophores that are useful for opto-electronic applications, with particularly application in light-emitting devices.

#1. A conjugated chromophore, as used herein, includes a linear conjugated organic compound or a polymer with at least 5 conjugated bonds, wherein protons linked to the conjugated bonds are partially or fully deuterated. Examples of typical backbones of conjugated chromophore compounds for this category can be described as in Scheme 1: