Local work function control of indium tin oxide by micro-contact printing for electroluminescent devices

Adjustment of the Work Function of Pyridine and Pyrimidine Substituted Aromatic Self-Assembled Monolayers by Electron Irradiation

“…The latter is demonstrated in Figure where representative examples of such patterns are presented. Consequently, e-beam lithography, which also has the advantages of a flexible form of the written features as well as dose variation across the pattern, can be a valuable alternative to other approaches to WF patterning such as microcontact printing. ,, Significantly, the dynamic range of the in situ variation of the WF covered by the PyPP1, TP1-up, and TP1-down SAMs is exceptionally large, viz. from +5.2 to +3.4 eV, with a small gap around +4.0 eV, between the minimal value for TP1-up/Au and the maximal value for TP1-down/Au (Figure a), which, however, can be covered by a proper mixed SAM of both these constituents .…”

Spatially Modulating Interfacial Properties of Transparent Conductive Oxides: Patterning Work Function with Phosphonic Acid Self‐Assembled Monolayers

“…[18,19] Fujihira and co-workers shifted the ITO work function using benzoyl-and phosphoryl-chlorides, [28,29] and microcontact printed these molecules to give patterned electroluminescence. [27] However, the resulting contact potential difference (CPD) contrast between patterned and unpatterned SAM regions of the ITO substrate was significantly lower than the CPD shift measured on ITO that had been soaked in a SAM solution, suggesting poorer ordering or lower density of the microcontact printed SAMs relative to solution-deposited SAMs. Blom and co-workers also observed lower-than-expected CPD contrast from an analogous microcontact printed thiol-SAM on gold system, reporting that their microcontact printed SAMs imparted a change in work function that was only 10% of the shift in work function achieved by solution deposition of the SAM.…”

“…[20][21][22][23][24][25][26] Given the strong influence SAM modifiers can have on the performance of organic electronic devices, the ability to microcontact print SAMs with large work function contrast is both scientifically interesting from the standpoint of creating model systems to explore the role of barriers and energy level offsets on charge injection in OLEDs, and technologically useful in the context of applications including low-cost illuminated signs and displays. [3,6] Although a limited amount of work has been performed in this area, notably by microcontact printing thiols on gold, [3,6] silanes on hydroxyl-terminated surfaces, [2,11,12] or phosphoryl chlorides on indium tin oxide (ITO), [27] these functional group/substrate combinations are not necessarily ideal for integration into OPV and OLED applications. First, transparent conductive oxides are more commonly used than gold as the anode in OPVs and OLEDs.…”

“…[23,33] Furthermore, the 0.55 V CPD contrast is ∼10× larger than the CPD previously reported using microcontact printed 4-chlorophenylphosphoryl dichloride on ITO. [27] We next evaluate the performance of the F 5 BnPA-microcontact printed ITO substrates as anodes in OLED devices incorporating the commercially available polymer Super Yellow (SY) (EMD Chemicals, PDY-132), with Ca/ Al as the top contacts. The device structure is depicted in Figure 1.…”

Structural Modifications in Bilayered Molecular Systems Lead to Predictable Changes in Their Electronic Properties

“…Following formation of bilayered systems on ITO, we analyzed how their molecular and geometrical properties affect electrode's work function. Literature reports suggest that polar or electrostatic SAMs can change the work function of the electrode by shifting up or down the vacuum level with the surface oriented dipole moment . Thus, polar moieties can be used to increase or decrease the work function through their electron‐withdrawing or donating properties and by controlling their distance from the electrode.…”