Incorporation of Spiroxanthene Units in Blue-Emitting Oligophenylene Frameworks: A New Molecular Design for OLED Applications
TL;DR: The incorporation of xanthenyl units into two extended π-conjugated phenylene systems, namely indenofluorene and pentaphenylene, which have been designed and synthesized through short and efficient synthetic approaches.
Abstract: We report herein the incorporation of xanthenyl units into two extended π-conjugated phenylene systems, namely indenofluorene and pentaphenylene. Thus, dispiroxanthene-indenofluorene (DSX-IF) and dispiroxanthene-ladderpentaphenylene (DSX-LPP) have been designed and synthesized through short and efficient synthetic approaches. These two molecules possess a 3π-2-spiro architecture (3π-systems/2-spiro bridges), in which two xanthenyl cores are spirolinked to a π-conjugated backbone either indenofluorene for DSX-IF or pentaphenylene for DSX-LPP. The structural, electrochemical, and photophysical properties of these blue/violet emitters have been studied in detail and compared to those of their 'all carbon' analogues with spirofluorenyl cores instead of spiroxanthenyl cores, namely dispirofluorene-indenofluorene (DSF-IF) and dispirofluorene-ladderpentaphenylene (DSF-LPP), previously reported in the literature. Finally, the application of DSX-IF and DSX-LPP as new light-emitting materials in nondoped organic light emitting diodes is reported. A detailed optical study of the different electroluminescence spectra is notably presented, with an emphasis 1) on the origin of the low-energy emission band observed in the case of DSX-LPP and 2) on the unexpected optical contribution of the well-known hole-transporting-layer NPB (N,N'-di(naphtyl)-N,N'-diphenyl(1,1'-biphenyl)-4,4'-diamine).
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20 Oct 2010TL;DR: In this paper, an electronic device comprising anode, cathode, and at least one organic layer which comprises a compound of the formula (I to (IV) is described.
Abstract: The present invention relates to an electronic device comprising anode, cathode and at least one organic layer which comprises a compound of the formula (I) to (IV). The invention furthermore encompasses the use of compounds of the formula (I) to (IV) in an electronic device and to a compound of the formula (Ic) to (IVc).
432 citations
TL;DR: In this article, two coordination complex emitters as well as host materials Be(PPI)2 and Zn-PPI2 (PPI = 2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol) are designed, synthesized, and characterized.
Abstract: Two coordination complex emitters as well as host materials Be(PPI)2 and Zn(PPI)2 (PPI = 2-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenol) are designed, synthesized, and characterized. The incorporation of the metal atom leads to a twisted conformation and rigid molecular structure, which improve the thermal stability of Be(PPI)2 and Zn(PPI)2 with high Td and Tg at around 475 and 217 degrees C, respectively. The introduction of the electron-donating phenol group results in the emission color shifting to the deep-blue region and the emission maximum appears at around 429 nm. This molecular design strategy ensures that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) HOMO and LUMO of Be(PPI)2 and Zn(PPI)2 localize on the different moieties of the molecules. Therefore, the two complexes have an ambipolar transport property and a small singlet-triplet splitting of 0.35 eV for Be(PPI)2 and 0.21 eV for Zn(PPI)2. An undoped deep-blue fluorescent organic light-emitting device (OLED) that uses Be(PPI)2 as emitter exhibits a maximum power efficiency of 2.5 lm W-1 with the CIE coordinates of (0.15, 0.09), which are very close to the National Television Standards Committee (NTSC) blue standard (CIE: 0.14, 0.08). Green and red phosphorescent OLEDs (PhOLEDs) that use Be(PPI)2 and Zn(PPI)2 as host materials show high performance. Highest power efficiencies of 67.5 lm W-1 for green PhOLEDs and 21.7 lm W-1 for red PhOLEDs are achieved. In addition, the Be(PPI)2-based devices show low-efficiency roll-off behavior, which is attributed to the more balanced carrier-transport property of Be(PPI)2.
135 citations
TL;DR: In this article, two star-shaped oligofluorenes, HFB-diF-Dpa and HFBterF-DPa, with a hexakis(fluoren-2-yl)benzene core and six diphenylamine end-cappers were designed and synthesized.
Abstract: Two new star-shaped oligofluorenes, HFB-diF-Dpa and HFB-terF-Dpa, with a hexakis(fluoren-2-yl)benzene core and six diphenylamine end-cappers were designed and synthesized. The peripheral diphenylamine groups enhance the HOMO energy levels of the materials, and the bulky star-shaped structures efficiently suppress the intermolecular interaction. Their thermal, photophysical, and electrochemical properties were investigated. The two compounds display strong deep-blue emission both in solution and solid state. Solution-processed devices based on these starbursts exhibit highly efficient and stable deep-blue electroluminescence. Their high-lying HOMO energy levels match very well with that of the hole-injecting material. The double-layered device featuring HFB-diF-Dpa as emitter shows a low turn-on voltage of 3.6 V, a maximum current efficiency of 6.99 cd A–1, and a maximum external quantum efficiency of 5.45% with the CIE coordinate of (0.154, 0.136). In particular, the combination of low driving voltage and...
112 citations
TL;DR: In this article, three aryl-substituted DiSpirofluorene-IndenoFluorenes (DSF-IFs 1, 3) possessing different fluorescent properties due to their different main emitters have been investigated through a structure-property relationship study.
Abstract: Intramolecular excimer emission arising from organic molecules as a blue light source in fluorescent Small Molecule Organic Light Emitting Diodes (SMOLEDs) is almost absent from the literature. In this work, three aryl-substituted DiSpiroFluorene–IndenoFluorenes (DSF–IFs 1–3) possessing different fluorescent properties due to their different main emitters have been investigated through a structure–property relationship study. Due to its particular geometry, the rigid DSF–IF platform 2 allows an ‘aryl/fluorene/aryl’ dimer to be preformed in the ground state leading, in the excited state, to a deep blue fluorescent emission through strong π–π intramolecular interactions between the two ‘aryl/fluorene/aryl’ arms. 2 has been successfully used as an emitting layer in a SMOLED with electroluminescence arising from electrogenerated intramolecular excimers and the properties of these excimer-based OLEDs have been compared to those of two model compounds (1 and 3). The simple and non-optimized double-layer device displays a deep blue colour (CIE coordinates: 0.19; 0.18) exhibiting a luminance of 510 Cd m−2 with a luminous efficiency of ca. 0.1 Cd A−1. This work is, to the best of our knowledge, the first rational and comparative study describing an intramolecular excimer based-SMOLED.
95 citations
TL;DR: In this article, triphenylene-based electron transport materials (ETMs) with coplanar molecular structure and a large electron affinity were designed and synthesized for use in organic light-emitting diodes (OLEDs).
Abstract: Triphenylene-based electron transport materials (ETMs), designated Bpy-TP1-4, with a coplanar molecular structure and a large electron affinity were designed and synthesized for use in organic light-emitting diodes (OLEDs). Spectroscopic ellipsometry measurements clarified that the deposited thin films of these ETMs have optical anisotropy, indicating that the molecules in the deposited thin films tend to be mostly oriented parallel to the substrate. Green OLEDs containing these ETMs allowed a lower driving voltage than that for OLEDs containing tris(8-hydroxyquinolinato)aluminum (Alq3) with a random orientation. In particular, the OLED containing Bpy-TP2 showed a significantly lower driving voltage, achieving lower power consumption when compared with conventional ETMs such as Alq3 and 1,3,5-tris(2-phenyl-1H-benzo[d]imidazol-1-yl)benzene (TPBi). Also, the operational lifetime of a blue OLED containing Bpy-TP2 is equivalent to that of an OLED with TPBi. The increased driving voltage of the device containing Bpy-TP2 is significantly suppressed compared to that of the OLED containing TPBi.
88 citations
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TL;DR: This paper could serve as a general literature citation when one or more of the open-source SH ELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
Abstract: An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.
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TL;DR: The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and signi®cant updates to existing ones.
Abstract: The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and signi®cant updates to existing ones. Following normal submission, a Computer Program Abstract will be reviewed by one or two members of the IUCr Commission on Crystallographic Computing. It should not exceed 500 words in length and should follow the standard format given on page 189 of the June 1985 issue of the Journal [J. Appl. Cryst. (1985). 18, 189± 190] and on the World Wide Web at http://www.iucr. org/journals/jac/software/. Lists of software presented and/or reviewed in the Journal of Applied Crystallography are available on the World Wide Web at the above address, together with information about the availability of the software where this is known.
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TL;DR: SIR97 is the integration of two programs, SIR92 and CAOS, the first devoted to the solution of crystal structures by direct methods, the second to refinement via least-squares–Fourier procedures.
Abstract: SIR97 is the integration of two programs, SIR92 and CAOS, the first devoted to the solution of crystal structures by direct methods, the second to refinement via least-squares–Fourier procedures. Several new features have been introduced in SIR97 with respect to the previous version, SIR92: greater automatization, increased efficiency of the direct methods section, and a powerful graphics interface. The program also provides publication tables and CIF files.
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TL;DR: School of Chemistry, Bio21 Institute, University of Melbourne, 30 Flemington Road, Victoria 3010, Australia; School of Materials Science and Engineering, Nanyang Technological University, Nastyang Avenue, Republic of Singapore 639798; Institute of Materials Research and Engineering (IMRE) and the Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
Abstract: A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.
2,378 citations
TL;DR: A comprehensive review of the literature on electron transport materials (ETMs) used to enhance the performance of organic light-emitting diodes (OLEDs) is presented in this article.
Abstract: A comprehensive review of the literature on electron transport materials (ETMs) used to enhance the performance of organic light-emitting diodes (OLEDs) is presented. The structure−property−performance relationships of many classes of ETMs, both small-molecule- and polymer-based, that have been widely used to improve OLED performance through control of charge injection, transport, and recombination are highlighted. The molecular architecture, electronic structure (electron affinity and ionization potential), thin film processing, thermal stability, morphology, and electron mobility of diverse organic ETMs are discussed and related to their effectiveness in improving OLED performance (efficiency, brightness, and drive voltage). Some issues relating to the experimental procedures for the estimation of relevant material properties such as electron affinity and electron mobility are discussed. The design of multifunctional electroluminescent polymers whereby light emission and electron- and hole-transport pro...
1,527 citations