Strain effects on the work function of an organic semiconductor

Area of Science:

• Materials Science
• Organic Electronics
• Solid-State Physics

Background:

• Understanding the relationship between mechanical strain and electronic properties is crucial for organic semiconductors.
• Flexible electronic devices are susceptible to various forms of strain, impacting their performance.
• Work function (WF) is a key parameter determining charge injection and device efficiency.

Purpose of the Study:

• To investigate the effects of tensile and compressive strain on the work function (WF) of rubrene single crystals.
• To establish a fundamental link between mechanical strain and the electronic properties of organic semiconductors.
• To explore strain-induced transitions in organic materials relevant to flexible electronics.

Main Methods:

• Quantification of mechanical strain using X-ray diffraction, analyzing thermal expansion mismatch.
• Measurement of work function changes via scanning Kelvin probe microscopy.
• Comparison of experimental results with density functional theory calculations.

Main Results:

• Work function of rubrene significantly increases with tensile strain and decreases with compressive strain.
• An elastic-to-plastic transition was observed at approximately 0.05% tensile strain along the π-stacking direction.
• Experimental findings qualitatively align with density functional theory predictions.

Conclusions:

• The study establishes the first concrete link between mechanical strain and the work function of an organic semiconductor.
• Results provide insights into the interplay between structural disorder and electronic properties in soft organic materials.
• Findings have significant implications for the design and stability of flexible organic electronic devices.