Thermally Activated "Cold" Holes Overcome Recombination Limits in Single-Component Organic Solar Cells With 15.6%...

Area of Science:

• Organic electronics
• Materials science
• Photovoltaics

Background:

• Single-component organic solar cells (SCOSCs) offer morphological stability but suffer from low efficiency due to rapid geminate recombination.
• Ultralong-lived charge-transfer (CT) states in these polymers are typically considered energetic traps, limiting performance.

Purpose of the Study:

• To develop a thermodynamic strategy to convert long-lived CT states into a resource for enhanced charge extraction in SCOSCs.
• To overcome the efficiency limitations imposed by non-radiative recombination in organic photovoltaics.

Main Methods:

• Engineered an interfacial energy ladder using a D18 polymer layer with a 0.02 eV highest occupied molecular orbital (HOMO) offset.
• Utilized thermal activation to promote and selectively harvest long-lived holes from the CT states.
• Optimized device architecture to manage interfacial energy levels.

Main Results:

• Achieved a record power conversion efficiency of 15.65% in optimized SCOSCs.
• Demonstrated successful outcompetition of non-radiative recombination loss through active energy management.
• Simultaneously improved open-circuit voltage, short-circuit current, and fill factor.

Conclusions:

• Established a new paradigm for organic photovoltaics by harnessing long-lived excited states as a thermal activation reservoir.
• Showcased a viable method to overcome thermodynamic recombination losses in SCOSCs.
• Highlighted the potential of strategic energy management for future high-efficiency organic solar cells.