Conformationally controlled ultrafast intersystem crossing in bithiophene systems

Area of Science:

• Organic electronics
• Photovoltaics
• Ultrafast spectroscopy

Background:

• Bithiophenes are model compounds for polythiophenes used in organic electronics and solar cells.
• Understanding excited-state dynamics is crucial for optimizing photovoltaic performance.

Purpose of the Study:

• To investigate the ultrafast dynamics of bithiophene systems.
• To elucidate the mechanism and influencing factors of intersystem crossing (ISC) in bithiophenes.
• To provide insights for designing efficient solar cell components.

Main Methods:

• Femtosecond time-resolved photoelectron spectroscopy was employed.
• Analysis focused on the symmetry of the S1 minimum energy geometry.
• Conformational effects on ISC rates were examined.

Main Results:

• Intersystem crossing in bithiophenes was confirmed to occur within picoseconds.
• ISC rates correlate with the symmetry of the S1 minimum energy geometry.
• The cis-conformer demonstrated a significantly higher ISC rate compared to the trans-conformer.

Conclusions:

• Molecular conformation critically influences intersystem crossing rates in bithiophenes.
• The cis-conformer's unique geometry enhances intersystem crossing.
• Findings offer principles for engineering materials with accelerated long-lived excited state formation for improved solar energy harvesting.