Fully Locked Conjugated Backbones in Simple-Structured Polymer Donors Enabling High-Performance Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Commercialization of organic solar cells (OSCs) requires cost-effective, wide-bandgap polymer donors.
• Polymer donors often exhibit conformational disorder due to rotatable sigma-bonds, hindering performance.
• Controlling polymer backbone conformation is crucial for optimizing optoelectronic properties.

Purpose of the Study:

• To investigate the impact of noncovalent conformational locks (NoCLs) on polymer donor structure and performance.
• To establish a structure-property-performance relationship for designing advanced polymer donors.
• To develop high-performance, cost-effective polymer donors for OSC applications.

Main Methods:

• Synthesis of simple-structured polymer donors (PBDT-TBT-X, X=H, F, Cl) with varying NoCLs.
• Systematic investigation of backbone conformation, optoelectronic properties, pre-aggregation, and charge transport.
• Fabrication and characterization of binary and ternary organic solar cell devices.

Main Results:

• A dual-locking strategy (S···O and S···Cl) resulted in a highly planar, fully locked polymer backbone (PBDT-TBT-Cl).
• PBDT-TBT-Cl achieved a binary OSC power conversion efficiency (PCE) of 16.11%, outperforming PBDT-TBT-H (6.35%) and PBDT-TBT-F (12.69%).
• Incorporating PBDT-TBT-Cl as a third component in ternary OSCs yielded a PCE exceeding 20%.

Conclusions:

• Fully locked polymer conformations are critical for achieving high performance in OSCs.
• Noncovalent conformational locks offer an effective strategy for designing high-performance, cost-effective polymer donors.
• This work provides a clear roadmap for optimizing polymer donor design through conformational control.