This thesis focused on modification and characterization of ITO substrates with carboxylic acid based self-assembled monolayers to improve OLED device performance. In this study, ITO was used as anode material in OLEDs. In order to modify ITO electrodes, MePIFA and DPIFA aromatic small molecules with double bound carboxylic acid have been used as self-assembly monolayer (SAM). Characterizations of modified ITO and unmodified ITO surfaces were performed via atomic force microscopy and scanning tunneling microscopy. In addition to surface characterization, I-V measurements of the modified and unmodified ITO were taken via spreading resistance microscopy and scanning tunneling microscopy. Moreover, in order to measure change in the surface potential after the modification of ITO surface with MePIFA and DPIFA SAM molecules, Kelvin Probe Force Microscopy was performed. Finally two different configurations of OLEDs devices were fabricated using thermal evaporator system in order to explore the effect of SAM modified ITO on electrical characterization of OLED devices. It was shown that OLED intensity, and turn on voltage were improved compared to OLED devices with unmodified ITO.