Interface Tuning between Two Connecting Bulk Heterojunctions in Small Molecule Bilayer Ternary Solar Cells

Area of Science:

• Organic Photovoltaics
• Materials Science
• Device Physics

Background:

• Bilayer ternary solar cells offer a novel approach to organic photovoltaic devices with triple-component active layers.
• These devices differ from traditional ternary bulk heterojunction (BHJ) blends, utilizing sequential deposition of two binary BHJs.
• Understanding interfacial effects is crucial for optimizing their performance.

Purpose of the Study:

• To investigate the fabrication and optimization of bilayer ternary solar cells.
• To explore the impact of the interface between binary BHJs on device power conversion efficiency (PCE).
• To analyze the role of an inserted C60 molecular monolayer at the interface.

Main Methods:

• Fabrication of bilayer ternary solar cells using metal phthalocyanine donors and fullerene acceptors.
• Sequential deposition of two binary BHJs.
• Insertion of a C60 molecular monolayer at the interface between the binary BHJs.
• Analysis of device performance and charge transport characteristics under negative bias.

Main Results:

• Direct stacking of BHJs severely restricted device efficiency.
• Inserting a C60 molecular monolayer between the binary BHJs significantly improved photovoltaic performance.
• The C60 interfacial layer demonstrated a positive effect on charge transport and recombination dynamics.

Conclusions:

• Interface engineering is critical for optimizing bilayer ternary solar cells.
• A C60 molecular monolayer effectively enhances charge transport and reduces recombination losses.
• This study highlights the unique influence of interfaces involving three materials in organic solar cells.