Achieving current rectification ratios ≥ 10⁵ across thin films of coordination polymer

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Fabricating thin films of coordination polymers (CPs), including metal-organic frameworks (MOFs), with sufficient electrical conductivity for device applications remains a significant challenge.
• Thin film configurations are essential for integrating CPs into functional electronic devices.

Purpose of the Study:

• To demonstrate a method for fabricating thin films of a copper(II)-coordination polymer (Cu(ii)-CP) with enhanced electrical properties.
• To investigate the effect of molecular doping on the conductivity and rectification behavior of Cu(ii)-CP thin films.
• To explore the potential of these modified thin films for electronic device applications.

Main Methods:

• Utilized a layer-by-layer assembly technique on a functionalized gold substrate with a self-assembled monolayer.
• Grew the Cu(ii)-CP at the solid-liquid interface to create open-metal sites.
• Employed molecular doping to activate these sites and modify film properties.

Main Results:

• Achieved significant enhancement in in-plane electrical conductivity of the Cu(ii)-CP thin film.
• Demonstrated an unprecedented cross-plane current rectification ratio exceeding 10⁵ at both room and elevated temperatures.
• Observed the formation of an electronic heterostructure in the molecularly doped thin film, responsible for the high rectification.
• Transformed the thin film's interfacial properties from hydrophilic to highly hydrophobic upon molecular doping.

Conclusions:

• The developed layer-by-layer method successfully produces conductive Cu(ii)-CP thin films suitable for electronic applications.
• Molecular doping is a viable strategy to dramatically enhance electrical conductivity and achieve high rectification ratios in CP thin films.
• The resulting electronic heterostructure exhibits performance comparable to commercial silicon rectifier diodes, highlighting the potential of CPs in advanced electronics.