21.26% Efficiency Organic Solar Cells Enabled by Mixed Self-Assembled Multilayers

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Self-assembled monolayers/multilayers (SAMs/SAMULs) are crucial for photovoltaic devices, but insufficient surface coverage limits their efficiency.
• The co-assembled SAMULs (Co-SAMULs) strategy, using guest molecules, offers a solution, yet the underlying mechanism requires further understanding.

Purpose of the Study:

• To investigate the working mechanism of guest molecules in Co-SAMULs for enhanced photovoltaic performance.
• To construct efficient Co-SAMULs using benzo[b]thien-2-ylboronic acid (BBA) as a guest and (4-(3,6-di(thiophen-3-yl)-9H-carbazol-9-yl)butyl) phosphonate (4PAThCz) as a host.

Main Methods:

• Co-assembly of BBA and 4PAThCz to form Co-SAMULs.
• Analysis of BBA's interaction with 4PAThCz micelles and its role during film formation.
• Fabrication and characterization of organic solar cells (OSCs) using the developed Co-SAMULs.

Main Results:

• BBA fused with 4PAThCz micelles, inhibiting growth and improving synergistic adsorption.
• Co-SAMULs formation led to significantly enhanced surface coverage and homogeneous film quality.
• The optimized OSCs achieved a champion power conversion efficiency (PCE) of 21.26% with a fill factor (FF) of 83.54%.

Conclusions:

• The study elucidates the mechanism of guest molecule integration in Co-SAMULs, highlighting BBA's role in improving surface coverage and film quality.
• The developed Co-SAMULs strategy effectively suppresses defects and enhances charge transport, leading to record-breaking performance in OSCs.