Effect of Isomerization on High-Performance Nonfullerene Electron Acceptors

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) require efficient electron acceptors for high performance.
• Isomeric molecular design offers a strategy to tune electronic and optical properties.
• Fused-ring systems are crucial for developing advanced electron acceptor materials.

Purpose of the Study:

• To design and synthesize novel isomeric fused-ring electron acceptors, FNIC1 and FNIC2.
• To investigate the structure-property relationships between the isomers.
• To evaluate their performance in organic solar cell applications.

Main Methods:

• Synthesis of two isomeric fused-nine-ring electron acceptors (FNIC1 and FNIC2).
• Characterization of electronic, optical, charge-transport, and morphological properties.
• Fabrication and testing of organic solar cells using PTB7-Th:FNIC1 and PTB7-Th:FNIC2 blends.

Main Results:

• FNIC2 exhibited red-shifted absorption, higher electron affinity, lower ionization energy, and enhanced electron mobility compared to FNIC1.
• Organic solar cells based on PTB7-Th:FNIC2 achieved a power conversion efficiency (PCE) of 13.0%, surpassing FNIC1-based devices (10.3%).
• Semitransparent devices with FNIC2 showed higher PCEs across various average visible transmittances (AVT) than those with FNIC1.

Conclusions:

• Isomeric modifications in fused-ring electron acceptors significantly impact their properties and device performance.
• FNIC2 represents a promising electron acceptor material for high-efficiency organic solar cells.
• The study highlights the potential of isomeric engineering for advancing organic photovoltaic technology.