Work function of fluorine doped tin oxide

Fluorine doped tin oxide (FTO) is a commonly used transparent conducting oxide in optoelectronic device applications. The work function of FTO is commonly cited as 4.4 eV, which is incommensurate with recent device performance results. Using x-ray photoelectron spectroscopy, the authors measured the work function of commercial FTO to be 5.0 +/- 0.1 eV. UV ozone treatment was found to increase the work function by similar to 0.1 eV due to surface band bending. The origins of the much lower work function previously reported are also discussed and are found to be a result of carbon contamination and UV induced work function lowering. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3525641]