Structural Homology Solid Additives Enhancing Crystallization Thermodynamics for Constructing Ordered Fibrillar...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Morphology control is crucial for advancing organic solar cells (OSCs) beyond the 20% efficiency barrier.
• Traditional additives can negatively impact the intrinsic polymer packing essential for high performance.

Purpose of the Study:

• To develop a new additive strategy for precise morphology regulation in layer-by-layer (LbL) processed OSCs.
• To overcome the limitations of conventional additives by employing a "structural homology" approach.

Main Methods:

• Designed an advanced additive (A2) through heteroatom engineering, based on the D18 polymer monomer (A1).
• Preserved alkylated bridges while replacing fused thiophenes with thiazoles in A2 for lattice compatibility.
• Incorporated electron-withdrawing imine nitrogen atoms into A2 to enhance its dipole moment and introduce specific conformational locks.

Main Results:

• The additive A2 acted as a homological template, optimizing crystallization thermodynamics for a highly ordered fibrillar network with improved π-π stacking.
• LbL-processed D18/L8-BO devices using A2 demonstrated accelerated exciton dissociation and reduced trap-assisted recombination.
• Achieved a record power conversion efficiency (PCE) of 20.22%, surpassing control (19.23%) and A1-processed (19.75%) devices.

Conclusions:

• The "structural homology" strategy with additive A2 effectively regulates morphology in LbL-processed OSCs.
• This method provides a pathway to break the efficiency bottleneck in organic solar cells.
• Heteroatom engineering of additives offers a promising route for developing high-performance organic electronic devices.