Variable-force tapping atomic force microscopy as a tool in the characterization of organic devices

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Tapping mode atomic force microscopy (AFM) is common for characterizing material phase separation.
• AFM surface imaging can be influenced by surface energy and tapping force, limiting bulk information.
• Accurate bulk characterization is crucial for optimizing material performance.

Purpose of the Study:

• To develop an improved method for imaging material phase separation in polymer mixtures.
• To investigate the bulk-phase separation of organic mixtures using variable-force AFM.
• To correlate AFM findings with the performance of organic electronic devices.

Main Methods:

• Employed variable-force atomic force microscopy (AFM) on organic mixtures.
• Recorded a series of AFM images at varying tapping forces.
• Analyzed the evolution of AFM phase images to infer bulk properties.

Main Results:

• Demonstrated the capability of variable-force AFM to sample materials both on the surface and in the topmost bulk.
• Showed that the analysis of evolving AFM phase images provides indirect information about bulk-phase separation.
• Found a strong correlation between variable-force AFM results and the performance of light-emitting electrochemical cells.

Conclusions:

• Variable-force AFM is an effective technique for indirectly probing bulk-phase separation in polymer mixtures.
• This method offers improved material characterization beyond surface-level analysis.
• The findings support the use of variable-force AFM for optimizing materials in organic electronic devices.