Regio-Regular Polymer Acceptors Enabled by Determined Fluorination on End Groups for All-Polymer Solar Cells with...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Small molecule acceptors (SMAs) are crucial for all-polymer solar cells (all-PSCs).
• End-group modification of SMAs influences their electronic properties and device performance.
• Previous work explored co-modified end groups; this study focuses on regiospecific isomers.

Purpose of the Study:

• To synthesize and characterize two regiospecific fluoro- and bromo- substituted end groups (IC-FBr-o & IC-FBr-m).
• To construct and evaluate two regio-regular polymer acceptors (PYF-T-o and PYF-T-m) based on these end groups.
• To investigate the impact of isomeric end-group configuration on all-PSC performance.

Main Methods:

• Synthesis and purification of novel fluoro- and bromo- substituted end groups.
• Construction of regio-regular polymer acceptors via polymerization.
• Fabrication and characterization of all-polymer solar cell devices using PM6:PYF-T-o and PM6:PYF-T-m blends.
• Analysis of optical absorption, morphology, charge transport, and device efficiency.

Main Results:

• PYF-T-o exhibited enhanced and bathochromic absorption compared to PYF-T-m.
• PYF-T-o demonstrated more ordered inter-chain packing and optimal phase separation with PM6.
• Devices based on PM6:PYF-T-o achieved a high power conversion efficiency (PCE) of 15.2%.
• Devices based on PM6:PYF-T-m showed significantly lower efficiencies (1.4%).

Conclusions:

• The configuration of end groups in polymer acceptors critically impacts photon harvesting, morphology, and charge dynamics.
• Regiospecific design of fluoro- and bromo- substituted end groups leads to high-performance all-PSCs.
• This work provides valuable guidelines for developing efficient regio-regular polymer acceptors for all-PSCs.