Dynamic Variation of Rectification Observed in Supramolecular Mixed Mercaptoalkanoic Acid

Area of Science:

• Molecular electronics
• Supramolecular chemistry
• Organic electronics

Background:

• Molecular electronics functionality requires aligning molecular orbital energy levels with the transmission window.
• Current approaches focus on designing molecules with accessible energy levels, facing challenges with defects and low breakdown voltages.
• Widening the transmission window is an alternative but technically difficult strategy.

Purpose of the Study:

• To demonstrate that supramolecular mixing can create tunable rectifiers from electro-inactive molecules.
• To investigate the impact of controlled monolayer packing on electrical properties.
• To overcome limitations of low breakdown voltages in molecular electronic components.

Main Methods:

• Formation of binary mixed monolayers using alkanethiolates with and without carboxylic acid head groups.
• Utilizing a surface-exchange reaction to create the mixed monolayer.
• Characterizing the electrical properties, including breakdown voltage and rectification behavior under external bias.

Main Results:

• A mixed monolayer withstands high voltages up to 4.5 V.
• The monolayer exhibits a dynamic rectification behavior dependent on bias magnitude and polarity.
• Sub-highest occupied molecular orbital (HOMO) levels are activated by the widened transmission window, explaining the observed properties.

Conclusions:

• Supramolecular mixing is a viable strategy to imbue new electrical properties into electro-inactive organic molecules.
• Controlled packing in mixed monolayers enhances device robustness and tunability.
• This approach offers a new pathway for designing advanced molecular electronic devices.