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

Abstract

The interface between an organic semiconductor and a transparent conducting oxide is crucial to the performance of organic optoelectronics. We use microcontact printing to pattern pentafluorobenzyl phosphonic acid self-assembled monolayers (SAMs) on indium tin oxide (ITO). We obtain high-fidelity patterns with sharply defined edges and with large work function contrast (comparable to that obtained from phosphonic acid SAMs deposited from solution).

Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified Phosphonic Acid Self‐Assembled Monolayers

“…An alternative approach to modify the WF is to shift the electrostatic potential at the surface via attachment of an electric dipole layer. Self‐assembled monolayers (SAMs) of various polar molecules have been intensively studied and successfully employed, both experimentally and theoretically, to modify the WF of different metals or metal oxides . For example, Hotchkiss et al applied a range of fluorinated benzyl phosphonic acids (BPAs) to tune the WF of ITO over 1.2 eV .…”

Modification of the Gallium‐Doped Zinc Oxide Surface with Self‐Assembled Monolayers of Phosphonic Acids: A Joint Theoretical and Experimental Study

“…Surface modification of inorganic electrode materials by organic molecules forming self‐assembled monolayers (SAMs) has been widely considered to tune the surface and interface properties in organic electronics applications . Recently, phosphonic acids (PA) have been used to modify the work function of both ITO and ZnO surfaces over a range greater than 1 eV . Electro‐absorption spectroscopy experiments on devices where a poly(p‐phenylenevinylene) derivative (“super yellow”) is used as the active layer, have also shown that the built‐in potential (V BI ) between the PA‐modified ITO surface and the active layer scales linearly with the work function of the PA‐modified ITO electrode .…”

“…While points (i) and (ii) have been discussed already in the case of PA‐modified ITO and ZnO surfaces in earlier theoretical and experimental studies, determining the energy‐level alignments usually remains very challenging when dealing with organic/inorganic interface systems. It is clear that a correct description of the energy level alignments of the molecular frontier orbitals with respect to the Fermi level or valence/conduction band edge of the electrode or interlayer is critical for understanding the charge injection/collection processes at these interfaces; however, many calculations based on density functional theory tend to present results that are not in good agreement with the experimental results coming, for instance, from photoelectron spectroscopy measurements.…”

Buffer and anode-integrated WO3-doped In2O3 electrodes for PEDOT:PSS-free organic photovoltaics

“…Although the choice of organic active materials and device structure is critical to the performance of an OSC, the importance of a stable transparent anode cannot be ignored because exciton formation and carrier extraction is significantly affected by the transmittance and resistivity of the transparent anode. To enhance the carrier extraction efficiency of conventional indium tin oxide (ITO) anodes, an additional buffer layer such as poly (3,4-ethylene dioxylene thiophene):poly (styrene sulfonic acid) (PEDOT:PSS) or a self-assembled monolayer has been deposited on the ITO anodes [7][8][9]. However, it is known that the acidic nature of the PEDOT:PSS layer leads to severe etching of the ITO and the diffusion of indium into the organic active layer, which in turn causes degradation of the OSC [10].…”