13.7% Efficiency Small-Molecule Solar Cells Enabled by a Combination of Material and Morphology Optimization

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Small-molecule solar cells (SMSCs) lag behind polymer solar cells in efficiency.
• Challenges include material matching and morphology control in SMSCs.

Purpose of the Study:

• To develop high-efficiency binary SMSCs.
• To investigate the impact of material properties and film morphology on device performance.

Main Methods:

• Utilized small molecules BSFTR and Y6 with matched absorption and energy levels.
• Employed sequential solvent vapor and thermal annealing for morphology optimization.
• Fabricated and characterized binary SMSC devices.

Main Results:

• Optimized blend films exhibited controlled crystallinity, balanced mobilities, and favorable phase separation.
• Achieved a record power conversion efficiency (PCE) of 13.69% for binary SMSCs.
• Obtained an open-circuit voltage of 0.85 V, short-circuit current of 23.16 mA cm⁻², and fill factor of 69.66%.

Conclusions:

• Matched small molecules and precise morphology control are crucial for high-performance SMSCs.
• This study sets a new benchmark for binary SMSC efficiency.
• Highlights the potential of carefully designed small molecules in organic photovoltaics.