In Situ Optical Studies on Morphology Formation in Organic Photovoltaic Blends

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cell efficiency relies heavily on bulk heterojunction (BHJ) blend film morphology.
• Morphology is governed by the complex interactions between donor, acceptor, and solvent during film formation.

Purpose of the Study:

• To investigate the in situ morphology evolution during blade coating of three distinct BHJ systems.
• To understand the drying and photoluminescence quenching dynamics during blend film formation.
• To establish the role of molecular weight in determining final blend film morphology.

Main Methods:

• Utilized a versatile in situ spectroscopy setup to monitor morphology evolution.
• Studied drying and photoluminescence quenching dynamics in pristine and BHJ films.
• Employed time-resolved photoluminescence (TRPL) as a novel in situ method for drying studies.

Main Results:

• Identified that the component with higher molecular weight dominates blend film formation and final morphology.
• Quantitatively determined dynamic and static quenching extents using in situ TRPL.
• Observed relative changes in quantum yield during the film formation process.

Conclusions:

• Provided fundamental insights into microstructure formation during the processing of various blend films.
• Demonstrated the utility of the presented in situ setup for developing blend inks.
• Highlighted the importance of understanding drying dynamics for solution-cast organic and hybrid electronics.