Mechanistic View on the Order-Disorder Phase Transition in Amphidynamic Crystals

Area of Science:

• Materials Science
• Solid-State Physics
• Organic Electronics

Background:

• Amphidynamic crystals are crucial for organic electronics, exhibiting unique order-disorder phase transitions.
• Understanding these transitions is key to controlling material properties and device performance.

Purpose of the Study:

• To elucidate the mechanistic understanding of order-disorder phase transitions in ditBu-BTBT and TIPS-pentacene.
• To identify lattice normal modes governing these transitions using experimental and computational methods.

Main Methods:

• Temperature-dependent low-frequency Raman spectroscopy to track lattice dynamics.
• First-principles calculations to model crystal behavior and phase transitions.
• Analysis of Raman peak position and width to identify critical lattice modes.

Main Results:

• Identified specific lattice normal modes associated with the order-disorder phase transition in ditBu-BTBT and TIPS-pentacene.
• DitBu-BTBT (2,7-di-tert-butylbenzo[b]benzo[4,5]thieno[2,3-d]thiophene) exhibited ideal behavior consistent with the 'hardcore mode' model.
• TIPS-pentacene (6,13-bis(triisopropylsilylethynyl) pentacene) showed deviations from the model due to strong inter-mode interactions.

Conclusions:

• The 'hardcore mode' model provides a framework for understanding phase transitions in these organic semiconductors.
• Differences in behavior between ditBu-BTBT and TIPS-pentacene stem from varying lattice mode interactions.
• Side-chain engineering is proposed as a strategy to control polymorphism and tune properties in amphidynamic crystals.