14.7% Efficiency Organic Photovoltaic Cells Enabled by Active Materials with a Large Electrostatic Potential...

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• Organic photovoltaic cells (OPVs) show promise but lag behind commercial solar cells in power conversion efficiency.
• A key challenge in OPVs is the high energy required to separate photogenerated electron-hole pairs.
• Developing efficient charge separation mechanisms is crucial for advancing OPV technology.

Purpose of the Study:

• To demonstrate a high-efficiency single-junction organic photovoltaic cell (OPV).
• To investigate the charge generation mechanism at a low driving force using specific materials.
• To explore the role of molecular electrostatic potential (ESP) in enhancing OPV performance.

Main Methods:

• Fabrication and testing of single-junction OPVs using a new polymer donor (PTO2) and nonfullerene acceptor (IT-4F).
• Ultrafast transient absorption spectroscopy to study charge pair dynamics and recombination.
• Theoretical studies to analyze molecular electrostatic potential (ESP) and intermolecular electric fields.

Main Results:

• Achieved a power conversion efficiency of 14.7% in the single-junction OPV.
• Demonstrated efficient charge generation with a low driving force.
• Observed formation of loosely bound charge pairs with extended lifetimes, reducing recombination.
• Theoretical analysis indicated a large molecular ESP between PTO2 and IT-4F, potentially aiding charge generation.

Conclusions:

• The new polymer donor PTO2 and nonfullerene acceptor IT-4F enable high-efficiency OPVs.
• Low driving force charge separation is achievable, leading to improved device performance.
• Molecular electrostatic potential (ESP) modulation is a promising strategy for further enhancing OPV efficiency.