Gas-Phase Organosilane Self-Assembled Monolayers on Indium Tin Oxide Electrodes: Effects of Terminal Groups and Deposition Temperature

Gas-phase thermal deposition was used to form three organosilane self-assembled monolayers on indium tin oxide (ITO) anodes: amine-terminated (NH2SAM), methyl-terminated (CH3SAM), and trifluoropropyl-terminated (F3SAM). Surface characterisation using water contact angle goniometry, ultraviolet photoelectron spectroscopy, and atomic force microscopy was combined with green organic light emitting diode (OLED) fabrication and J–V–L measurements to determine how terminal group chemistry and deposition time affect device performance. F3SAM increased the ITO work function from 3.72 to 4.47–4.72 eV, resulting in ultrasmooth surfaces (Rₐ = 0.20 nm) and a maximum luminescence of ~6000 cd m−2, eleven times higher than bare ITO (540 cd m−2). CH3SAM enhanced luminescence through surface passivation at 10 min (3374 cd m−2), but decreased quickly with extended deposition durations due to multilayer roughening. NH2SAM reduced the work function to 3.42 eV and gradually decreased hole injection, resulting in a turn-on voltage of 10–11 V after 180 min. These results indicate that terminal group polarity and deposition duration are the two most important parameters in gas-phase SAM engineering of ITO anodes for OLEDs.