Medium Bandgap Conjugated Polymer for High Performance Polymer Solar Cells Exceeding 9% Power Conversion Efficiency

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Development of efficient and stable organic solar cells is crucial for renewable energy.
• Medium-bandgap polymers are promising candidates for photovoltaic applications.
• Benzo[1,2-b:4,5-b']dithiophene and 2,1,3-benzothiadiazole are common building blocks in polymer solar cells.

Purpose of the Study:

• To synthesize and characterize novel medium-bandgap polymers for polymer solar cells.
• To investigate the relationship between polymer structure, morphology, and photovoltaic performance.
• To achieve high power conversion efficiency in single-junction polymer solar cell devices.

Main Methods:

• Synthesis of two novel medium-bandgap polymers incorporating benzo[1,2-b:4,5-b']dithiophene and 2,1,3-benzothiadiazole units with a 6-octyl-thieno[3,2-b]thiophene π-bridge.
• Analysis of polymer properties including highest occupied molecular orbital (HOMO) energy levels, crystallinity, and bulk-heterojunction morphology.
• Fabrication and testing of single-junction polymer solar cell devices to evaluate photovoltaic performance.

Main Results:

• The synthesized polymers exhibit deep HOMO energy levels, indicating good stability.
• High crystallinity and optimal bulk-heterojunction morphology were observed, facilitating efficient charge transport.
• A power conversion efficiency (PCE) of up to 9.44% was achieved for the single-junction polymer solar cell devices.

Conclusions:

• The developed medium-bandgap polymers demonstrate excellent photovoltaic properties.
• The combination of deep HOMO levels, high crystallinity, and optimized morphology leads to high device performance.
• These findings highlight the potential of these novel polymers for efficient and stable polymer solar cells.