Random Terpolymerization as a Design Strategy to Modulate Aggregation in NDI-Based Polymer Acceptors for All-Polymer...

Area of Science:

• Materials Science
• Polymer Chemistry
• Renewable Energy

Background:

• Naphthalene diimide (NDI)-based conjugated polymers are key components in all-polymer solar cells (all-PSCs).
• Strong self-aggregation of these polymers can lead to detrimental phase separation and suboptimal donor-acceptor mixing.
• Controlling polymer aggregation is crucial for enhancing the performance of all-PSCs.

Purpose of the Study:

• To investigate the effect of random terpolymerization on the aggregation behavior of NDI-based polymer acceptors.
• To enhance the performance of all-polymer solar cells by modulating polymer aggregation.
• To synthesize and characterize novel terpolymers for all-PSC applications.

Main Methods:

• Synthesis of four terpolymers (PNDI-T21, PNDI-T23, PNDI-T25, PNDI-RT) via random terpolymerization, incorporating thiophene derivatives into a reference polymer (PNDI-T2).
• Characterization of polymer aggregation and crystallinity influenced by thiophene content and backbone randomness.
• Fabrication and performance evaluation of all-polymer solar cells using the synthesized terpolymers as acceptors.

Main Results:

• Terpolymerization modulated backbone planarity and aggregation, with increased thiophene content generally enhancing aggregation.
• A highly randomized backbone structure was found to reduce both aggregation and crystallinity.
• The terpolymer with the weakest aggregation (PNDI-T21) exhibited the highest power conversion efficiency (5.3%) in all-PSCs.
• The terpolymer with the strongest aggregation (PNDI-T25) showed the lowest power conversion efficiency (3.2%).

Conclusions:

• Random terpolymerization is an effective strategy to control the aggregation of NDI-based polymer acceptors.
• Optimizing polymer aggregation through controlled terpolymerization can significantly improve all-PSC performance.
• The balance between aggregation and backbone structure is critical for achieving high efficiency in all-polymer solar cells.