Chemically Installed Organic Metal Nucleation Inducers on Molecular Materials for Ultrathin Metal Electrodes

Metal aggregation is a general challenge in deposition of ultrathin metal electrodes on the molecular materials in OLEDs and organic solar cells. Nucleation inducers attached to the thin-film material are effective means to address the aggregation issue. Nucleation inducers enable affixation of different functional groups, optimized to bind to a particular metal electrode, onto the surface. In this dissertation, chemical reactions are used to install organic Metal Nucleation Inducers (o-MNIs) on molecular materials. Surface modification has been applied to two categories of materials: heteroatom containing and non-heteroatom containing materials. Accordingly, o-MNIs are applied to the surface of pentacene and TPBi. In its most optimal demonstration, applying different inducers to the surface of pentacene decreases the sheet resistance of a deposited silver electrode significantly and shifts the percolation threshold thickness from 11 nm to 8 nm. The smooth, continuous, electrode generated at low thicknesses highlights the suppression of the Volmer-Weber growth mode, as observed by scanning electron microscopy. Effectiveness was lower on TPBi, a heteroatom containing molecular material, due to competing nucleation within the molecular material itself. As the second part of the dissertation, MADN, a non-heteroatom containing semiconductor, has been chosen to be tested as an ETL layer in an OLED stack to determine the compatibility of o-MNI with device applications. A 9 nm Ag electrode deposited on MADN treated surface displays 72% optical transmittance and sheet resistance of 8.7 Ω/sq. The close turn-on voltages and overall similarity in performance suggest utilization of o-MNI are compatible with OLED applications and the o-MNI seems to be a promising methodology.