Probing Ternary Solvent Effect in High V(oc) Polymer Solar Cells Using Advanced AFM Techniques

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Perovskite solar cells (PSCs) are promising for renewable energy.
• Developing high-performance PSCs requires understanding nanoscale material properties.
• Existing characterization methods may not fully capture the complexities of the active layer.

Purpose of the Study:

• To present a simple method for developing high open-circuit voltage (V(oc)) low band gap PSCs.
• To introduce novel atomic force microscopy (AFM)-based techniques for nanoscale characterization of PSC active layers.
• To correlate nanoscale morphology and properties with device performance.

Main Methods:

• Ternary solvent processing for active layer and C60 buffer layer fabrication.
• Pulsed-Force-Mode AFM (PFM-AFM) for surface morphology and physical properties.
• Mode-Synthesizing AFM (MSAFM) for visualizing donor-acceptor phases.
• Conductive AFM (cAFM) for local conductivity and photocurrent mapping.

Main Results:

• A bulk heterojunction PSC with V(oc) > 0.9 V and 7.5% conversion efficiency was achieved.
• MSAFM enabled sensitive visualization of donor-acceptor phases within the active layer.
• cAFM revealed local conductivity variations and increased photocurrent in ternary solvent-processed PTB7:ICBA samples.

Conclusions:

• Ternary solvent processing is an effective method for enhancing PSC performance.
• Advanced AFM techniques provide critical insights into the nanoscale structure-property relationships in PSCs.
• Understanding and controlling nanoscale features are key to optimizing PSC efficiency.