Improved cation valence state in molybdenum oxides by ultraviolet-ozone treatments and its applications in organic light-emitting diodes

Abstract

The authors demonstrate a thick MoO3 layer (60 nm) as a good short reduction layer in organic light emitting diodes (OLEDs), which is especially useful for large-area and flexible OLEDs to prevent short circuit issues. The crystallization of organic material and the increase of driving voltage induced by a thick MoO3 layer in OLEDs were resolved by a simple ultraviolet-ozone (UV-ozone) treatment. Ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, contact angle, and atomic force microscope analyses revealed that a longer UV-ozone treatment resulted in an optimized fraction of oxygen vacancies in MoO3, which is responsible for the improved device performance. © 2013 AIP Publishing LLC.