Volatile Imide Additives with Large Dipole and Special Film Formation Kinetics Enable High-Performance Organic Solar...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Large dipole moment additives improve organic solar cell (OSC) morphology and performance.
• Strong intermolecular interactions of traditional additives hinder their removal, potentially affecting device stability.
• Developing volatile additives with high dipole moments for OSCs remains a significant challenge.

Purpose of the Study:

• To report novel volatile imide additives for enhancing OSC performance through morphology modification.
• To investigate the effect of positional isomerization of halogen atoms on molecular configuration and interactions.
• To explore the unique film formation kinetics induced by these additives.

Main Methods:

• Screening of three N-(chlorophenyl)phthalimide (ClPA) additives (oClPA, mClPA, pClPA) with varying dipole moments.
• Analysis of molecular configuration and intermolecular interactions.
• Investigation of film formation kinetics, specifically nucleation and crystal growth.
• Fabrication and performance testing of organic solar cells using these additives.

Main Results:

• ClPAs exhibit larger dipole moments (2.0664 to 4.7896 Debye) compared to existing solid additives.
• ClPAs induce a unique film formation process: acceptor nucleation followed by growth, leading to improved crystallinity.
• Power conversion efficiency (PCE) of OSCs improved from 16.13% to 18.58% with pClPA in a PM6:BTP-eC9 system.
• High PCEs of up to 19.04% were achieved in other systems (PM6:L8-BO, PM6:Y6, D18:L8-BO) with pClPA.

Conclusions:

• Imide-based volatile additives offer a simple and effective strategy for improving OSC performance.
• Positional isomerization of halogen atoms significantly impacts molecular interactions and photovoltaic performance.
• The unique film formation kinetics induced by ClPAs are crucial for achieving high-quality morphology and enhanced device efficiency.