Heterogeneous Nucleating Agent for High-Boiling-Point Nonhalogenated Solvent-Processed Organic Solar Cells and...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• High-boiling-point nonhalogenated solvents offer processing advantages for large-area organic solar cells (OSCs) but cause aggregation issues with small molecule acceptors like L8-BO, reducing efficiency.
• Controlling molecular aggregation is crucial for optimizing the morphology and performance of OSC active layers.

Purpose of the Study:

• To develop a novel strategy to overcome the aggregation problem of small molecule acceptors in high-boiling-point nonhalogenated solvents for OSC fabrication.
• To improve the nucleation and crystallization processes within the OSC active layer to achieve higher power conversion efficiencies (PCEs) and operational stability.

Main Methods:

• Grafting oligo(ethylene glycol) side-chains onto L8-BO to create a modified acceptor, BTO-BO, with lower formation energy.
• Utilizing BTO-BO as a heterogeneous nucleating agent in the active layer blend (PM6:L8-BO) to promote controlled crystallization.
• Investigating the effect of strong hydrogen bonding interactions between BTO-BO and L8-BO on nucleation density and phase separation.

Main Results:

• BTO-BO significantly increases nucleation density, leading to suppressed excessive aggregation and ideal phase-separated morphology with small domain sizes and high crystallinity.
• Toluene-processed OSCs using this strategy achieved a record PCE of 19.42% (certified 19.12%) with enhanced operational stability.
• The method demonstrated scalability, yielding a 15.03 cm² module with a record PCE of 16.35% (certified 15.97%).

Conclusions:

• The heterogeneous nucleating agent strategy using BTO-BO effectively controls molecular aggregation and improves active layer morphology in OSCs processed with high-boiling-point nonhalogenated solvents.
• This approach provides a viable pathway for fabricating high-efficiency, stable, and large-area organic solar cells using environmentally friendly solvents.