Direct Laser Writing Crystal Polymorphs of Organic Semiconductors for Phase Change Electronics.

Area of Science:

• Organic electronics
• Materials science
• Crystallography

Background:

• Organic electronic materials exhibit diverse polymorphic behaviors.
• Polymorphism allows modulation of electronic properties via crystal structure switching.
• Two-dimensional quinoidal terthiophene displays prolific polymorphism.

Purpose of the Study:

• To access and control polymorphic phases in two-dimensional quinoidal terthiophene using laser writing.
• To investigate the electronic property modulation achievable through laser-induced phase transitions.
• To demonstrate the application of laser writing for device fabrication and tuning.

Main Methods:

• Laser writing was employed for localized heating and directing phase transitions.
• Grazing incidence X-ray diffraction (GIXD) was used to analyze crystal symmetry and packing.
• Raman spectroscopy confirmed phase transitions and material properties.
• Fabrication and testing of transistor devices were performed.

Main Results:

• A metastable polymorph IV was accessed through rapid cooling.
• Distinct symmetry and packing of polymorph IV were characterized by GIXD.
• Laser heating induced a reversible transition from polymorph IV to I.
• Conductance switched by over two orders of magnitude.
• Transistor devices demonstrated switching and discrete conductance tuning via laser writing.

Conclusions:

• Laser writing provides a precise method to control polymorphism in organic electronic materials.
• Reversible switching of crystal structures leads to significant modulation of electronic properties.
• This technique offers a pathway for fabricating and tuning organic electronic devices with tailored functionalities.