The aluminum on polythiophene interface

Although polythiophene may not be presendy one of the most attractive materials for polymer-based LEDs, it has played an important role in LED development. For example, the first polymer-LED with a significant degree of polarized light was fabricated from a substituted polythiophene15. From the experimental interface standpoint, two of the more promising thiophene systems 

The Al(2p) spectra for aluminum on P30T, as a function of the coverage, are shown in Fig. 7.4. These spectra exhibit two interesting features. First, the main Al(2p) line gradually shifts towards lower binding energy as the thickness of the aluminum layer increases. This is a consequence of the improved core-hole screening for 

A detailed analysis of the UPS spectra of pristine P3HT, (where H = hexyl) based on the results of VEH quantum-chemical calculations of the density-of-valence-states, the DOVS, has been presented previously27. For the present purposes, the UPS results on P3HT and P30T are the same the differences in the length of the aliphatic side 

The aluminum deposition also induces dramatic changes in the 

These theoretical results discussed in the preceding paragraph are fully consistent with the experimental XPS and UPS data. Indeed, the new features appearing on the C(ls), S(2p), and Al(2p) XPS spectra constitute dear evidence of the charge transfer from aluminum to carbon and sulphur. Other model configurations, where the aluminum atoms are made to interact either only with the sulphur atoms or only with the 0-carbon atoms, are calculated to be much less stable than the Al—C structure described above, and do not result in any electron density redistribution consistent with the XPS results. The inert character of the 0-carbons, and of the adjacent thiophene units, upon reaction of aluminum with a given thiophene unit also is reflected in the spectra, as the major part of the C(ls) and S(2p) contribution remains unshifted when aluminum is deposited 

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