Efficient and Nonhalogenated Solvent-Processed Organic Solar Cells Enabled by Conjugated Donor-Acceptor Block...

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Organic solar cells (OSCs) offer a low-cost, flexible alternative to silicon-based photovoltaics.
• Conjugated block copolymers (CBCs) enable simple one-pot solution processing for OSCs.
• Improving power conversion efficiencies (PCEs) and reducing reliance on toxic solvents are key challenges in OSC development.

Purpose of the Study:

• To develop a novel conjugated block copolymer (CBC) for efficient and stable OSCs.
• To demonstrate a halogen-free solution process for fabricating high-performance OSCs.
• To compare the performance of CBC-based OSCs with binary polymer blends and conjugated random copolymers (CRCs).

Main Methods:

• Synthesis of a new (D1-A1)-b-(D1-A2)-type CBC, PBDB-T-b-PY5BDT, featuring shared benzodithiophene (BDT) units.
• Fabrication of OSC devices using a halogen-free solution process.
• Characterization of photovoltaic performance, mechanical stability, thermal stability, and storage stability.

Main Results:

• The PBDB-T-b-PY5BDT-based OSCs achieved a high PCE of 10.55%.
• The CBC-based devices exhibited excellent mechanical, thermal, and storage stabilities.
• OSCs based on PBDB-T-b-PY5BDT demonstrated superior photovoltaic performance, stability, and mechanical robustness compared to binary polymer blends and CRCs.

Conclusions:

• The developed CBC, PBDB-T-b-PY5BDT, enables efficient and stable OSCs via a halogen-free process.
• Shared BDT units in the donor and acceptor blocks mitigate unfavorable interfacial interactions, enhancing performance.
• CBC-based OSCs represent a promising advancement over traditional polymer blend and CRC-based devices.