When the Substrate Matters in Solar Cells: Photoinduced Force Microscopy Uncovers How ITO Pretreatment Governs...

Area of Science:

• Materials Science
• Surface Chemistry
• Renewable Energy

Background:

• Self-assembled monolayers (SAMs) are crucial hole-selective layers in perovskite and organic solar cells.
• Previous research focused on preventing micelle formation in precursor solutions, neglecting substrate anchoring effects during film deposition.

Purpose of the Study:

• To investigate the role of substrate anchoring sites on indium tin oxide (ITO) during SAM film deposition.
• To understand how substrate pretreatment methods influence SAM aggregation, orientation, and subsequent solar cell performance.

Main Methods:

• Utilized photoinduced force microscopy (PiFM) to spatially correlate structural information of SAMs on different ITO substrates.
• Compared solar cell performance using SAMs deposited on UV-ozone treated versus O2 plasma-treated ITO substrates.

Main Results:

• UV-ozone treatment of ITO promoted SAM micelle aggregation and face-on adsorption.
• O2 plasma treatment provided denser anchoring sites, suppressing micelle nucleation and favoring edge-on SAM orientation.
• Solar cells fabricated on O2 plasma-treated substrates demonstrated superior performance compared to those on UV-ozone treated substrates.

Conclusions:

• Substrate pretreatment significantly affects SAM formation and solar cell efficiency, challenging the notion that UV-ozone treatment always yields optimal SAMs.
• A competitive mechanism involving molecular self-aggregation and anchoring site density governs SAM formation.
• Optimizing substrate anchoring is a critical factor for enhancing solar cell performance.