Over 19 % Efficiency Organic Solar Cells Enabled by Manipulating the Intermolecular Interactions through Side Chain...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Non-fullerene acceptors (NFAs) are crucial for organic solar cell (OSC) performance.
• Fluorine side chain functionalization is a known strategy to enhance OSCs, but structure-property relationships require further investigation.

Purpose of the Study:

• To investigate the impact of fluorine functionalization on the side chains of Y-series NFAs.
• To establish a clear relationship between structural modifications and device performance in organic solar cells.

Main Methods:

• Synthesized two NFAs, BTP-F0 and BTP-F5, with varying fluorine content in their side chains.
• Employed theoretical and experimental methods to analyze electrostatic potential, molecular packing, and bulk-heterojunction morphology.
• Fabricated and characterized organic solar cell devices using the synthesized NFAs.

Main Results:

• Side-chain fluorination increased average electrostatic potential and charge balance, enhancing intermolecular interactions.
• Fluorinated NFAs (BTP-F5) led to improved crystallinity, domain purity, and vertical phase distribution in OSCs.
• BTP-F5 based OSCs achieved power conversion efficiencies (PCE) of 17.3% (binary) and 19.2% (ternary), outperforming BTP-F0 based devices (16.1% PCE).

Conclusions:

• Fluorine functionalization of Y-series NFA side chains is an effective strategy for tuning molecular packing and morphology.
• Optimized morphology facilitates exciton diffusion, reduces charge recombination, and improves charge extraction in OSCs.
• This study provides a structure-performance relationship for designing high-efficiency organic solar cells through side-chain engineering.