Structure-Function Relationships in PMA and PMAT Series Copolymers for Polymer Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Donor-acceptor copolymers are crucial for bulk heterojunction (BHJ) polymer solar cells (PSCs).
• Understanding structure-property relationships is key to optimizing PSC performance.

Purpose of the Study:

• To design and synthesize two series of 2D donor-acceptor copolymers (PMA and PMAT) with varying conjugated side chain lengths and acceptor end groups.
• To investigate the structure-function relationships of these copolymers for BHJ PSC applications.

Main Methods:

• Synthesis of PMA and PMAT copolymer series.
• Characterization of electronic and photophysical properties (absorption, HOMO/LUMO levels).
• Fabrication and performance testing of BHJ PSC devices using [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as acceptor.

Main Results:

• Copolymers exhibited broad visible absorption with two distinct peaks.
• Increasing electron-withdrawing strength of acceptor groups red-shifted intramolecular charge transfer.
• PMAT series copolymers, with longer conjugated side chains, achieved higher power conversion efficiencies (PCEs) ranging from 3.14–4.01% compared to PMA series (2.05–2.16%).

Conclusions:

• Side chain length and acceptor end groups significantly influence copolymer electronic properties and PSC performance.
• Fine-tuning the chemical structure of donor-acceptor copolymers is an effective strategy for enhancing BHJ PSC efficiency.