Mobility-controlled performance of thick solar cells based on fluorinated copolymers

Area of Science:

• Materials Science
• Photovoltaics
• Polymer Chemistry

Background:

• Enhancing polymer solar cell (PSC) efficiency necessitates understanding structure-property relationships.
• Device characteristics are influenced by numerous parameters, complicating direct structure-property analysis.
• Developing efficient and scalable PSCs requires tailored material design.

Purpose of the Study:

• To investigate the impact of fluorine substitution in copolymers on photovoltaic properties.
• To identify key parameters governing the fill factor in bulk heterojunction (BHJ) polymer solar cells.
• To establish structure-property correlations for optimizing PSC performance.

Main Methods:

• Fabrication of BHJ photovoltaic devices using a series of copolymers with varying fluorine content.
• Characterization of photovoltaic properties, focusing on fill factor and charge generation/recombination.
• Analysis of polymer molecular ordering and its correlation with charge transport.

Main Results:

• Hole mobility was identified as the primary determinant of fill factor in thick BHJ devices.
• Increased fluorine substitution led to enhanced hole mobility, attributed to improved polymer molecular ordering.
• Charge generation efficiency and recombination coefficients remained largely consistent across the copolymer series.

Conclusions:

• Achieving high hole mobility is critical for maximizing fill factor in thicker PSCs.
• Molecular ordering significantly influences charge transport properties in PSC materials.
• Combining high mobility with suppressed recombination is essential for scalable PSC technologies.