Modifying the Surface Properties of Indium Tin Oxide with Alcohol-Based Monolayers for Use in Organic Electronics

Abstract

Transparent conductive oxides serve a critical function in many devices, such as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs). To optimize the performances of these devices, it is desirable to tune the interface between the transparent conductive oxide (TCO) and the next functional layer of these devices. Self-assembled monolayers prepared from phosphonic acids and silanes are commonly used to tune the properties and performance of this interface, including its surface energy, work function, and durability. Here, we report a new form of self-assembled monolayers for modifying indium tin oxide (ITO), a standard TCO used in OLEDs and OPVs. The ITO surfaces were modified with a series of distinct alcohol reagents.Stabilities of these alcohol based monolayers were compared with modifications derived from silanes and phosphonic acids, which are commonly used in the literature and industrial processes. Work functions and surface energies of these modified substrates were determined using ultraviolet photoelectron spectroscopy and contact angle measurements. Stability of these monolayers were assessed using cyclic voltammetry, X-ray photoelectron spectroscopy, and transmission spectroscopy techniques. Based on the results of these studies, alcohol based monolayers are promising candidates to modify ITO substrates for use in OLEDs and OPVs.

Using Spectator Ligands to Enhance Nanocrystal-to-Molecule Electron Transfer

“…In the first (left), spectator ligands containing static dipole moments produce an electric field that, depending on its alignment, will raise or lower the free energy for transferring a charge from a NC to a molecule bound to its surface. This approach of binding polar molecules to a surface has been used to tune the work function of planar semiconductors employed for solar energy and fuels generation − and was recently utilized by Beard and co-workers to vary the work function of PbS NCs over a 2 eV range . However, while increasing Δ G ° for photoinduced NC-to-molecule charge transfer can improve its rate, it will come at a cost as a smaller fraction of an absorbed photon’s energy will be stored in the resulting products.…”

Patterning Indium Tin Oxide Using Self-Assembled Monolayers as Etch Resists for Photovoltaic and Display Devices

“…As shown in 6b. 17,28 Here, former studies also reported that the inorganic oxide surface of In−O−In/Sn appears at 530.0 eV, 17,23 while lattice oxygen ions appear at 529.5 eV. 23 Thus, in brief, the results shown in Figure 6 are similar to former findings (e.g., Kim et al, 28 ); it indicates that the PA SAM treatment resulted in an organic−inorganic (ODP−ITO) interface bond, and the UV−ozone exposure successfully removed the PA SAMs over the ITO surface.…”

Tuning the Surface Chemistry of Second-Harmonic-Active Lithium Niobate Nanoprobes Using a Silanol–Alcohol Condensation Reaction

“…This molecular reagent was attached to the NPs through a silanol–alcohol condensation reaction (as outlined in Figure ). The hydroxyl (R–OH) group of 12-HDA underwent a condensation reaction with the Si–OH groups on the SiO x coating to form silyl ether (Si–O–R) bonds on the surfaces of the NPs. − This reaction was performed by suspending the NPs and the 12-HDA in propylene carbonate. This polar aprotic reagent has been demonstrated to be a good solvent for performing silanol–alcohol condensation reactions over a range of alcohol-containing reagents .…”

“…An alternative approach to functionalize the surfaces of materials uses alcohol-containing reagents. The silanol–alcohol condensation reaction can be used to modify the surface chemistry of a variety of substrates (e.g., silica, alumina, indium tin oxides). − Alcohol (R–OH) reagents are an alternative class of molecules to the silane-based reagents that have been more widely used to functionalize the surfaces of silica. A number of alcohol-containing molecules can be covalently bound to surfaces of SiO x through the silanol–alcohol condensation reaction, forming stable silyl ether (Si–O–C) bonds. , Alcohol-based reagents have several advantages over silane-based precursors for modifying the surfaces of materials.…”

“…A number of alcohol-containing molecules can be covalently bound to surfaces of SiO x through the silanol–alcohol condensation reaction, forming stable silyl ether (Si–O–C) bonds. , Alcohol-based reagents have several advantages over silane-based precursors for modifying the surfaces of materials. Advantages of using alcohol-based reagents include their relative stability to moisture, their mono-reactivity, and their widespread availability in different molecular forms with a variety of functional groups. − Such alcohol-based molecular reagents have been covalently bound to silica surfaces to create new surface functionalities, such as amines, aldehydes, fluorocarbons, nucleic acids, thiols, and cyanides. − Adding these functional groups to a material provides a platform for the covalent attachment of biologically important molecules (e.g., polyethylene glycols or PEGs, antibodies, fluorescent molecules) that can be used in a diverse range of applications (e.g., bioimaging, drug delivery, biosensing).…”