High-Lying 3¹A_g Dark-State-Mediated Singlet Fission

Area of Science:

• Photophysics and Materials Science
• Organic Electronics
• Quantum Chemistry

Background:

• Singlet fission (SF) converts one singlet to two triplets, boosting photovoltaic efficiency.
• Low-lying dark states in SF chromophores can act as intermediates or traps, complicating SF processes.
• Understanding dark-state photophysics is crucial for optimizing SF materials.

Purpose of the Study:

• Investigate a new photophysical model involving a high-lying dark state in SF.
• Characterize the role of the 3¹A_g dark state in benzodipyrrolidone (BDPP) SF.
• Explore BDPP as a potential material for efficient photovoltaic devices.

Main Methods:

• Transient spectroscopy for time-resolved measurements.
• Multireference electronic structure calculations (XDW-CASPT2) for theoretical analysis.
• Combined experimental and computational approach to study dark-state dynamics.

Main Results:

• Identified a high-lying 3¹A_g dark state mediating ultrafast SF in BDPP.
• The 3¹A_g state, with multiexciton character, is populated from the 1¹B_u bright state.
• BDPP exhibits favorable optical and triplet properties, high triplet yield, and photostability.

Conclusions:

• The 3¹A_g dark state plays a key role in ultrafast SF in BDPP.
• BDPP is a promising candidate for SF-based photovoltaic applications.
• Findings advance the understanding of dark-state photophysics and SF material development.