Photoluminescence and electroluminescence of oligoacetylenic silanes and germanes

Liming Ding, Wai Yeung WONG, Hongqi Xiang, Suk Yue Poon, Frank E. Karasz*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

15 Citations (Scopus)


A series of light-emitting oligoacetylenic silanes and germanes containing fluorene units was investigated. It was found that the higher oligomers display lower band gaps and that the CSi(Ge)C bond permits π-electron delocalization. The π-dSi or π-dGe interactions aid the π-electrons in passing through the Si (Ge) atoms. The observed differences in fluorescence spectra may also result from a substituent effect of the silyl groups. The SiSi σ bond also permits π-electron delocalization and thus there is a through-bond interaction between π orbitals and the SiSi bond. The conjugation-interrupting Ge sp3 link aids π-electron delocalization along the oligomer backbone less efficiently than does a Si link, thus leading to relatively shorter effective conjugation lengths and higher band gaps. In the higher oligomers, multiple π-dSi or π-d Ge interactions permit the vibrational levels of the excited state to split to form sublevels observable as new transitions in the respective absorption spectra. FWHM values of the PL spectra increase with increase of the oligomer backbone length which relates to the increase of the intermolecular interaction between the chromophore units. With increasing oligomer backbone length, the EL efficiency decreases, which can be attributed to the enhanced probability of interchain exciton annihilation in LEDs using higher oligomers.

Original languageEnglish
Pages (from-to)110-116
Number of pages7
JournalSynthetic Metals
Issue number2-4
Publication statusPublished - 1 Feb 2006

Scopus Subject Areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

User-Defined Keywords

  • π-Electron delocalization
  • Conjugation length
  • Electroluminescence
  • Light-emitting diodes
  • Oligoacetylenic silanes and germanes
  • Photoluminescence


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