Interspersed Assembled Monolayers Enhance Hole Transport in High-Efficiency Organic and Perovskite Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Nanotechnology

Background:

• Self-assembled monolayers (SAMs) are crucial for organic and perovskite solar cells.
• Micelle formation in SAMs can hinder device performance.
• Optimizing interfacial energy and film morphology is key to high efficiency.

Purpose of the Study:

• To introduce and evaluate interspersed assembled monolayers (IAMs) as a strategy to suppress micelle formation.
• To investigate the impact of dispersant backbone (NNN, NSN) and side-chain length on solar cell performance.
• To elucidate the mechanisms behind IAMs' performance enhancement in organic solar cells (OSCs) and perovskite solar cells (PSCs).

Main Methods:

• Design and synthesis of IAMs with varying dispersant backbones (NNN, NSN) and side chains.
• Fabrication and characterization of OSCs (PM6:Y6, PM6:L8-BO) and PSCs incorporating IAMs.
• Utilized femtosecond transient absorption and time-resolved photoluminescence spectroscopy to study underlying mechanisms.

Main Results:

• IAM strategy significantly improved power conversion efficiencies (PCE) in both OSCs and PSCs compared to traditional SAMs.
• The NSN backbone, with its larger dipole moment, generally led to higher PCEs (e.g., 18.04% in PM6:Y6 OSCs, 25.01% in PSCs).
• Short-side-chain IAMs demonstrated comparable performance to long-side-chain variants, indicating design flexibility.

Conclusions:

• IAMs effectively suppress micelle formation, leading to enhanced charge extraction, reduced recombination, and improved film morphology.
• Both the conjugated backbone and side chains of IAM molecules are critical for optimizing performance.
• IAMs offer a stable and practical approach for developing high-performance organic and perovskite solar cells.