β-Disubstituted Pentacene Derivatives: Thin Film Structural Properties and Four-Probe Field Effect Mobility

Area of Science:

• Organic electronics
• Materials science
• Semiconductor physics

Background:

• Pentacene is a benchmark organic semiconductor for organic field-effect transistors (OFETs).
• Diphenyl substitution is known to enhance charge carrier mobility in polycyclic aromatic hydrocarbons like anthracene.
• Investigating substituted pentacenes is crucial for developing advanced organic electronic materials.

Purpose of the Study:

• To synthesize 2,9- and 2,10-diphenylpentacene isomers.
• To evaluate their performance as active components in organic field-effect transistors (OFETs).
• To understand the impact of diphenyl substitution position on molecular packing and charge transport properties.

Main Methods:

• Synthesis via direct C-H borylation, halodeboronation, Suzuki arylation, and decarbonylation.
• Thin film fabrication using vapor deposition on SiO2 substrates.
• Characterization of molecular packing and measurement of 4-probe hole mobilities in OFETs.

Main Results:

• Both 2,9- and 2,10-diphenylpentacene isomers were successfully synthesized and formed nanoribbons during thin film growth.
• The 2,9-isomer exhibited similar molecular packing and a hole mobility of 0.13 cm2 V−1 s−1, comparable to unsubstituted pentacene.
• The 2,10-isomer showed detrimental effects on molecular ordering, resulting in a lower hole mobility of 0.07 cm2 V−1 s−1.

Conclusions:

• 2,9-Diphenylpentacene preserves the thin-film characteristics and performance of unsubstituted pentacene in OFETs.
• 2,10-Diphenylpentacene substitution significantly disrupts molecular ordering, leading to reduced field-effect mobility.
• The mobility enhancement seen in diphenylanthracene cannot be directly translated to pentacene through these substitution patterns.