Degradation mechanisms of polyfluorene-based organic semiconductor lasers under ambient and oxygen-free conditions

  • chair:

    Brenner, P. / Fleig, L., M. / Liu, X. / Welle, A. / Bräse, S. / Lemmer, U. (2015)
  • place:

    Journal of Polymer Science Part B. Polymer Physics, (2015), 53, 1029-1034
  • Date: April 2015

Abstract

In this communication we investigate the degradation mechanisms of different highly fluorescent polyfluorenes for applications as active organic semiconductor material in laser devices. Using various analytical methods, like Ultraviolet-Visible (UV-Vis) absorption spectroscopy, Fouriertransform infrared spectroscopy (FT-IR) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), we investigate photo-induced degradation mechanisms.

It is shown that the photo-oxidation rate decreases with an increasing number of benzothiadiazole units within the conjugated polymer. Photooxidation is much more distinct for poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) than for poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,10,3}-thiadiazole)] (F8BT).

The influence of the photooxidation on the lifetime of the organic laser devices is not as profound as previously assumed, since the laser shuts down before any evidence of photo-oxidation in F8BT manifests. We observe that the solubility of the material is different at various degradation levels and we consider chain scission of excited bonds and cross- linking as dominant degradation factors.

 

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