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

This study uses a novel surface engineering approach to demonstrate the influence of organic functional group substitutions on molecular electronic properties. Specifically, bilayered organic monomolecular systems immobilized on an inorganic electrode as the charge-injecting components of organic electronic devices are compared. Recent literature reports demonstrate that structural modification in functional monolayers have unpredictable effects on their electronic properties. These studies indicate that the structure most certainly plays an important role, but its effect on the molecular resistance is diminished due to differences in other monolayer parameters. It is demonstrated that a separate control over the monolayer geometry and its chemical structure is required in order to observe predictable structure-property relations. Here, bilayered molecular interfaces, comprising inert and functional layers whose properties can be independently controlled, are formed. It is shown that 1) the charge transfer through the bilayered system is sensitive to small structural molecular changes; 2) that it can be controlled and predicted by controlling the electron-withdrawing or donating nature of the organic moiety; and 3) that the differences in the charge transfer dynamics of two bilayered systems can be visualized via patterned electroluminescence.