Achieving Uniform Phase Structure for Layer-by-Layer Processed Binary Organic Solar Cells with 20.2% Efficiency

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Layer-by-layer (LBL) deposition is a promising technique for fabricating organic solar cells (OSCs).
• Characterizing and optimizing the 3D morphology of LBL-processed active layers remains a challenge.
• The correlation between LBL morphology and photovoltaic properties is not well understood.

Purpose of the Study:

• To investigate the morphology and formation mechanisms of LBL-processed active layers using the D18/L8-BO blend.
• To understand how morphology influences the photovoltaic properties of organic solar cells.
• To explore the role of additives in controlling the nanomorphology.

Main Methods:

• Systematic investigation of morphology and formation mechanisms in LBL-processed D18/L8-BO active layers.
• Utilizing blend casting for comparison with traditional bulk heterojunction (BHJ) films.
• Analyzing the effect of the solid additive DBM on the nanomorphology.

Main Results:

• A unique 3D nanomorphology with a uniform, "zigzag"-shaped phase structure was achieved in LBL-processed active layers.
• The solid additive DBM, with its twisted conformation, was identified as crucial for uniform phase structure formation.
• The 3D morphology significantly improved the short-circuit current and fill factor of the OSCs.
• An impressive power conversion efficiency (PCE) of 20.2% was achieved in the binary device.

Conclusions:

• Layer-by-layer deposition enables unique 3D nanomorphologies in organic solar cell active layers.
• The additive DBM plays a critical role in controlling and optimizing this 3D nanomorphology.
• The achieved 3D nanomorphology directly correlates with enhanced photovoltaic performance in OSCs.