Stepwise heating in Stille polycondensation toward no batch-to-batch variations in polymer solar cell performance

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Batch-to-batch variations in molecular weight (M_w) and polydispersity index (Ð) of π-conjugated polymers lead to inconsistent material properties and device performance.
• Controlling polymer quality is crucial for the commercialization of organic solar cells.

Purpose of the Study:

• To develop a facile and effective strategy for synthesizing ultrahigh-quality semiconducting polymers.
• To improve the performance and reduce variations in polymer-based solar cells.

Main Methods:

• A stepwise-heating protocol in Stille polycondensation was employed to synthesize PTB7 polymer.
• Optimized processing techniques were used in conjunction with the polymerization protocol.
• Fabrication and testing of polymer-based solar cells using the synthesized ultrahigh-quality PTB7.

Main Results:

• Ultrahigh-quality PTB7 polymer with high M_w and very narrow Ð was obtained.
• Polymer-based solar cells achieved up to 9.97% power conversion efficiencies (PCEs), a >24% enhancement over control devices.
• Negligible batch-to-batch variations in PCE values were observed for devices made with the ultrahigh-quality polymer.

Conclusions:

• The stepwise polymerization strategy is effective for producing high-quality semiconducting polymers.
• This approach significantly improves device yield and mitigates device-to-device variations in organic solar cells.
• The findings contribute to the commercialization of organic solar cells by enhancing reliability and performance.