Determination of the charge neutrality level of poly(3-hexylthiophene)

The Al/poly(3-hexylthiophene) (P3HT) and Ag/P3HT interfaces were investigated using photoemission spectroscopy in combination with in situ thin-film deposition. The P3HT thin films were deposited directly into high vacuum from solution on the two metal substrates using an electrospray system and characterized via photoemission spectroscopy. The electronic structure and charge injection barriers at these interfaces were determined from the evaluation of the resulting spectra sequences. A linear correlation between barrier heights and substrate work functions was observed from the collected data in combination with previously published results, suggesting that the "Induced Density of Interfaces States" model for small molecular materials is also valid for conjugated polymer interfaces. The corresponding P3HT "screening factor" as well as its charge neutrality level was determined to be 0.48 and 3.44 eV, respectively.