1 Ocak 2019 Dergi makalesi Açık Erişim

Usta, Hakan; Alimli, Dilek; Ozdemir, Resul; Dabak, Salih; Zorlu, Yunus; Alkan, Fahri; Tekin, Emine; Can, Ayse

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  <dc:creator>Usta, Hakan</dc:creator>
  <dc:creator>Alimli, Dilek</dc:creator>
  <dc:creator>Ozdemir, Resul</dc:creator>
  <dc:creator>Dabak, Salih</dc:creator>
  <dc:creator>Zorlu, Yunus</dc:creator>
  <dc:creator>Alkan, Fahri</dc:creator>
  <dc:creator>Tekin, Emine</dc:creator>
  <dc:creator>Can, Ayse</dc:creator>
  <dc:date>2019-01-01</dc:date>
  <dc:description>The development of solution-processable fluorescent small molecules with highly efficient deep-blue electroluminescence is of growing interest for organic light-emitting diode (OLED) applications. However, high-performance deep-blue fluorescent emitters with external quantum efficiencies (EQEs) over 5% are still scarce in OLEDs. Herein, a novel highly soluble oligo(p-phenyleneethynylene)-based small molecule, 1,4-bis((2-cyanophenyl)ethynyl)-2,5-bis(2-ethylhexyloxy)benzene (2EHO-CNPE), is designed, synthesized, and fully characterized as a wide band gap (2.98 eV) and highly fluorescent (Phi(PL) = 0.90 (solution) and 0.51 (solid-state)) deep-blue emitter. The new molecule is functionalized with cyano (-CN)/2-ethylhexyloxy (-OCH2CH(C2H5)C4H9) electron-withdrawing/-donating substituents, and ethynylene is used as a pi-spacer to form an acceptor (A)-pi-donor (D)-pi-acceptor (A) molecular architecture with hybridized local and charge transfer (HLCT) excited states. Physicochemical and optoelectronic characterizations of the new emitter were performed in detail, and the single-crystal structure was determined. The new molecule adopts a nearly coplanar pi-conjugated framework packed via intermolecular "C-H center dot center dot center dot pi" and "C-H center dot center dot center dot N" hydrogen bonding interactions without any pi-pi stacking. The OLED device based on 2EHO-CNPE shows an EQE(max) of 7.06% (EQE = 6.30% at 200 cd/m(2)) and a maximum current efficiency (CEmax) of 5.91 cd/A (CE = 5.34 cd/A at 200 cd/m(2)) with a deep-blue emission at CIE of (0.15, 0.09). The electroluminescence performances achieved here are among the highest reported to date for a solution-processed deep-blue fluorescent small molecule, and, to the best of our knowledge, it is the first time that a deep-blue OLED is reported based on the oligo(p-phenyleneethynylene) pi-framework. TDDFT calculations point to facile reverse intersystem crossing (RISC) processes in 2EHO-CNPE from high-lying triplet states to the first singlet excited state (T-2/T-3 -&gt; S-1) (hot-exciton channels) that enable a high radiative exciton yield (eta(r) similar to 69%) breaking the theoretical limit of 25% in conventional fluorescent OLEDs. These results demonstrate that properly designed fluorescent oligo(p-phenyleneethynylenes) can be a key player in high-performance deep-blue OLEDs.</dc:description>
  <dc:identifier>https://aperta.ulakbim.gov.trrecord/90747</dc:identifier>
  <dc:identifier>oai:zenodo.org:90747</dc:identifier>
  <dc:rights>info:eu-repo/semantics/openAccess</dc:rights>
  <dc:rights>http://www.opendefinition.org/licenses/cc-by</dc:rights>
  <dc:source>ACS APPLIED MATERIALS &amp; INTERFACES 11(47) 44474-44486</dc:source>
  <dc:title>Highly Efficient Deep-Blue Electroluminescence Based on a Solution-Processable A-pi-D-pi-A Oligo(p-phenyleneethynylene) Small Molecule</dc:title>
  <dc:type>info:eu-repo/semantics/article</dc:type>
  <dc:type>publication-article</dc:type>
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