Modifications in organic electronic devices: Uncovering the mechanisms of performance enhancement using interfacial self assembled monolayers

Organic light emitting diodes (OLEDs) are fabricated and characterized on anodes modified by a variety of surface treatments. OLED performance response is correlated to the treatment conditions with current-voltage (I-V) measurements and impedance spectroscopy. Small-scale OLED arrays are fabricated using a novel shadow mask approach and are characterized with electrical measurements, and the observation and sources of device-to-device variations are probed. An additional fabrication procedure for small-scale OLEDs via soft lithography is attempted, and a new approach to patterning soft lithographic stamps is developed. Finally, the electrical properties of self-assembled monolayers (SAMs) are studied in response to changes in the substrate surface and electrode composition.; This study begins with an examination of the macro-scale OLED performance response to a variety of anode surface treatments. The inclusion of a SAM at the anode/organic interface dramatically influences the transient behavior of the diode, as observed via impedance spectroscopy and subsequent equivalent circuit analysis. A thorough investigation of OLED response to changes in device geometry has allowed the creation of a detailed OLED equivalent circuit model. Variations in the OLED anode cleaning procedures, interpreted with the aid of an equivalent circuit model, have afforded additional insight into the mechanism of performance enhancement upon the inclusion of a SAM. The presence of charge traps at the anode/organic interface hinders the establishment of a uniform electrode field across the diode, and passivation of charge traps through the inclusion of SAMs or through proper surface treatment improves OLED performance and efficiency.; After elucidation of the detailed OLED equivalent circuit model, the size of the OLEDs was reduced to sub-micron dimensions through the use of a novel shadow mask fabrication scheme. Patterned suspended-membrane silicon nitride shadow masks with sub-micron dimensions have been fabricated by combing electron beam lithography (EBL) and traditional semiconductor processing. In addition, two new atomic force microscopy (AFM) techniques have been developed to characterize sub-micron diodes, atomic force electroluminescence microscopy (AFEM) and bridge-enhanced nano-scale impedance microscopy (BE-NIM). AFEM allows the traditional OLED performance metrics (I-V plots) to be gathered for devices <250 nm in diameter, while BE-NIM facilitates investigation of the impedance response of the diodes. When combined, these two AFM techniques demonstrate the persistence of charge traps at the sub-micron scale, and it is observed that differences in charge trap density account for previously unexplained local performance variations in small-scale OLED arrays.; An additional approach to fabricate small-scale OLEDs has been previously demonstrated using soft lithography. Here, a new route to soft lithographic PDMS stamp fabrication is developed using EBL. EBL allows for rapid, master-less patterning of PDMS stamps with micro-scale features, and a thorough investigation of the patterning process and mechanism have been performed. Through EBL the chemical functionality of PDMS stamps is modified, as verified by secondary ion mass spectrometry. Additionally, several soft lithographic applications utilizing EBL patterned PDMS stamps are demonstrated.; Finally, the performance response of another class of electronic devices, capacitors, are optimized and evaluated using SAMs on silicon surfaces. A reduction in the number of low-capacitance layers in a multi-layer organic dielectric structure is predicted to increase the capacitance of the resulting devices. To facilitate this increase a new dielectric molecule is synthesized, characterized, and utilized in organic capacitors on the hydrogen-passivated silicon <111> surface. An analogous series of capacitor structures are fabricated on silicon with a native oxide surface, and I-V scans and...