Ultrathin Self-Assembled Monolayer for Effective Silicon Solar Cell Passivation.

Area of Science:

• Materials Science
• Photovoltaics
• Surface Chemistry

Background:

• Passivation is critical for crystalline silicon (c-Si) solar cell performance, requiring thin layers for efficient carrier transport.
• Existing ultrathin passivated contact structures in Silicon Heterojunction (SHJ) and Tunnel Oxide Passivated Contact (TOPCon) cells exceed 26% efficiency.
• Organic passivation offers cost reduction and process simplification but faces environmental safety challenges.

Purpose of the Study:

• To introduce a low-cost, environmentally friendly organic passivation material for c-Si solar cells.
• To investigate the interfacial properties and performance enhancement offered by the new material.
• To provide insights into developing novel passivation methods for future solar cell technologies.

Main Methods:

• Synthesis and characterization of a novel self-assembled monolayer (SAM) material, 2PACz ([2-(9H-carbazol-9-yl) ethyl] phosphonic acid).
• Fabrication of c-Si solar cells utilizing the 2PACz passivation layer.
• Analysis of the chemical bonding (P-O-Si) and electronic properties (hole-selectivity) of the ultrathin film.

Main Results:

• The 2PACz SAM forms stable P-O-Si bonds on the silicon surface.
• The carbazole group in 2PACz provides electron-localizing and hole-selective properties.
• The passivation engineering effectively repairs porous silicon surfaces and reduces losses, improving solar cell performance.

Conclusions:

• 2PACz is a promising, low-cost, and environmentally safe alternative for c-Si solar cell passivation.
• This material enables high-efficiency ultrathin film passivation, offering a pathway for dopant-free silicon solar cells.
• The findings pave the way for next-generation passivation techniques in the post-silicon era.