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Abstract The surface potential of a prototypical organic semiconductor, pentacene, is chemically modified by the addition of a dipole monolayer on top of the thin film. Changes are afforded by reacting the topmost layer of pentacene to generate the monolayer, and the reactant structure provides a high degree of tunability for surface potential, with shifts up to 800 mV possible. Despite the complexity of the adsorbed layer, the surface potential shift displays a near‐linear dependency between dipole strength and surface potential change, and a good degree of predictability via the Helmholtz equation. The large changes in surface potential should be enough to access electron injection in thisp‐type semiconductor, but deviceI–Vcharacteristics are not consistent with this behavior. Interactions between the metal top contact and a chemical functional group within the monolayer are the likely culprit, with spectroscopic evidence presented. While tailoring the surface potential of organic surfaces is achievable, maintaining the integrity of surface energetics upon metal deposition remains challenging. 

Pentacene thin-films OFETs show increased conductance and mobility after exposure to maleic anhydride which shifts the mean energy in the grain boundaryviaan applied dipole. 

Adlayers are often placed at metal-on-organic interfaces as a common strategy to alleviate damage during metal deposition by thermal evaporation. Methods of chemically installing adlayers have been recently demonstrated on organic semiconductors that address these interfacial issues while providing many secondary benefits. Chemical installation has yet to be attempted at the cathode-electron transport layer (ETL) interface within organic light-emitting devices (OLEDs), offering a powerful option to optimize electron injection, improve surface wetting, and reduce metal penetration. Here, a reaction between TPBi (2,2′,2′’-(1,2,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) and propylene oxide results in a controllable 1–3 nm thick layer of propylene oxide as shown by high-resolution X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The reactive addition of the adlayer at temperatures below 40℃ does not affect the morphology of the thin film and reaches a high degree of coverage within 3 h. Integration of this layer into a phosphorescent OLED does not introduce any significant negative impact on device function. This result opens up the possibility of introducing further specific functionality into the adlayer to engineer OLED performance.