Achieving Record-Efficiency Organic Solar Cells upon Tuning the Conformation of Solid Additives

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Volatile solid additives (SADs) are crucial for tuning film morphology in high-performance organic solar cells (OSCs).
• The precise structural impact of SADs on photovoltaic performance remains incompletely understood.

Purpose of the Study:

• To investigate the influence of SAD conformation on the morphology and photovoltaic performance of organic solar cells.
• To design and synthesize novel volatilizable SADs with distinct structural features.

Main Methods:

• Synthesis of two SADs: SAD1 (twisted conformation) and SAD2 (planar with S···O noncovalent intramolecular interactions).
• Theoretical calculations and experimental characterization to analyze molecular packing and film morphology.
• Fabrication and testing of single-junction binary OSCs using the synthesized SADs.

Main Results:

• Planar SAD2, with its smaller space occupation, effectively facilitated tighter intermolecular packing of Y6 molecules post-thermal treatment.
• SAD2-treated OSCs demonstrated reduced recombination losses, improved charge mobility balance, and enhanced hole transfer rates.
• A record power conversion efficiency (PCE) of 18.85% (certified 18.7%) was achieved for single-junction binary OSCs treated with SAD2.

Conclusions:

• The conformation of SADs significantly impacts the morphology and photovoltaic performance of OSCs.
• Planar SADs with specific noncovalent interactions offer a promising strategy for optimizing OSC performance.
• This study provides valuable insights into structure-property relationships for SADs in organic electronics.