Catechol-Functionalized Self-Assembled Monolayer for Highly Efficient Sn─Pb and All-Perovskite Tandem Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• All-perovskite tandem solar cells rely on Sn-Pb narrow-bandgap subcells for performance.
• Self-assembled monolayers (SAMs) like 2PACz are successful in lead-based PSCs but limited in Sn-Pb PSCs due to poor extraction and stability.
• Existing SAMs face challenges in carrier extraction and interfacial stability for Sn-Pb perovskite solar cells (PSCs).

Purpose of the Study:

• To design and introduce a novel SAM, DOPhCz, for Sn-Pb PSCs.
• To investigate the impact of DOPhCz on perovskite nucleation, crystallinity, and interfacial properties.
• To enhance the performance and operational stability of Sn-Pb PSCs and all-perovskite tandem solar cells.

Main Methods:

• Design and synthesis of a new SAM, 9-(3,4-dihydroxyphenyl)-9H-carbazole (DOPhCz), with a catechol anchoring group.
• Incorporation of DOPhCz into Sn-Pb PSCs and comparison with 2PACz-based devices.
• Characterization of perovskite film properties, interfacial defects, carrier extraction, and device performance and stability.

Main Results:

• DOPhCz SAMs promote homogeneous perovskite nucleation and improved crystallinity, reducing interfacial defects.
• DOPhCz-based Sn-Pb PSCs achieve a 24.17% power conversion efficiency, surpassing 2PACz-based devices (22.87%).
• DOPhCz enhances hole extraction, reduces chemical perturbation, and significantly improves operational stability, with tandem cells reaching 28.30% efficiency.

Conclusions:

• DOPhCz is a promising SAM for high-performance Sn-Pb PSCs and all-perovskite tandem solar cells.
• The study elucidates a mechanism for SAM-induced interfacial stabilization in perovskite solar cells.
• Molecular engineering of SAMs offers valuable strategies for developing advanced perovskite solar cell technologies.