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Current injection in organic semiconductors remains difficult to predict due in large part to the challenge of characterizing the contact energy barrier and interface density of states directly in organic electronic devices. Here, resonant coupling to surface plasmon polariton modes of a metal contact is demonstrated as a means to carry out internal photoemission (IPE) accurately in disordered organic semiconductor devices and enable direct measurement of the contact injection barrier by isolating true IPE from spurious sub-gap organic photoconductivity. The substantial increase in sensitivity afforded by resonant coupling enables measurement in the low-field injection regime where deviation from the standard Fowler prediction is explained quantitatively by the existence of a broad distribution of interface states. This technique is broadly applicable to metals and surface treatments commonly used in organic light emitting diodes, thin film transistors, and photovoltaics, and should therefore provide a quantitative basis to understand and model current injection in these devices over their entire operational lifetime. [ABSTRACT FROM AUTHOR]

Highlights: [•] A cross-linkable hole transporting material for OLEDs has been demonstrated. [•] The resulting devices have a higher efficiency and smaller efficiency roll-off compared with NPB-devices. [•] The resulting devices have a longer lifetime. [Copyright &y& Elsevier]

Latest developments in solution processed hole injection layer (HIL) technology that has enabled near-ohmic injection into OLED stacks will be presented. Some of the advantages inherent to solution processing will be demonstrated including the planarization of low cost engineered OLED substrates. [ABSTRACT FROM AUTHOR]

A new aqueous based polymer, Plexcore® OC AQ1200 (AQ1200) was used as a hole injection layer (HIL) in organic light emitting diodes (OLEDs) and the device results are compared with polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) in terms of injection efficiency and stability. Dark injection transient measurements show a higher injection efficiency in hole-only devices using AQ1200 HIL compared with PEDOT:PSS. Using AQ1200 as an HIL, high efficiency phosphorescent OLEDs are demonstrated to have a long lifetime, with an estimated operational half lifetime (LT 50) of more than 8000 h from an initial luminance of 1000 cd/m 2 . [ABSTRACT FROM AUTHOR]