X-Ray Spectroscopy of Organic Materials
A study of oligothiophene-based molecular semiconductor materials with potential applications in light-emitting and photovoltaic devices is undertaken. Angle-resolved NEXAFS measurements of the star-shaped 4(HPBT) molecules on an amorphous indium surface show a strong dichroic signal indicating a well-ordered, uniformly upright arrangement of planar molecules. The X-ray excited optical luminescence (XEOL) measurements showed several sharp features associated with vibronic splitting of the LUMO-HOMO luminescent transition. The HOMO-LUMO gap determined from the XEOL measurements is 2.28 eV; this value is in agreement with previously published optical measurements as well as with the value that is estimated from the combination of NEXAFS and X-ray emission spectroscopy (XES) measurements. Films formed from blended solutions of 4(HPBT) and the hole-transporting molecular semiconductor PCBM are shown to form a bilayer structure with the PCBM adjacent to the substrate. Annealing causes desorption of the 4(HPBT) from the surface.
Advisor:Moewes, Alex; Chang, Gap Soo; Koustov, A.; Pickering, I.; Tse, J.; Hirose, A.; Heske, C.
School:University of Saskatchewan
School Location:Canada - Saskatchewan
Source Type:Master's Thesis
Keywords:molecular spectroscopy chemical physics synchrotron
Date of Publication:06/29/2009