Buried Interface Modulation via Molecular Dipole Passivation for High-Efficiency Methylammonium-Free Pb-Sn Perovskite...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Methylammonium-free (MA-free) lead-tin perovskite solar cells (PSCs) show promise for next-generation photovoltaics due to tunable bandgaps.
• Key challenges include Sn²⁺ oxidation and poor energy-level alignment at interfaces, limiting efficiency and stability.

Purpose of the Study:

• To develop a dipole passivation strategy to improve the performance and stability of MA-free Pb-Sn PSCs.
• To address interfacial defects and degradation issues in Pb-Sn PSCs.

Main Methods:

• A dipole passivation strategy using 4-(trifluoromethyl) benzamidine hydrochloride (TFBA) was introduced at the PEDOT: PSS/perovskite interface.
• TFBA passivates defects and inhibits acidity-induced degradation via hydrogen-bonding and coordination interactions.

Main Results:

• The TFBA-modified interface resulted in high-quality Pb-Sn perovskite films and improved energy-level alignment.
• Optimized Pb-Sn PSCs achieved a power conversion efficiency (PCE) of 22.48%, with a record V_oc × FF of 0.894 V × 81.74%.
• Unencapsulated devices retained 88.7% efficiency after 1500 hours in N₂.

Conclusions:

• TFBA dipole passivation effectively enhances the efficiency and stability of MA-free Pb-Sn PSCs.
• The strategy overcomes critical interfacial limitations, paving the way for advanced perovskite solar cell technologies.