Dual-Function Halide Exchange Strategy for Simultaneous Sn⁴⁺ Elimination and Stability Enhancement in Pb-Sn Mixed...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Lead-tin (Pb-Sn) mixed perovskites are crucial for high-efficiency all-perovskite tandem solar cells.
• Sn2+ oxidation to Sn4+ creates defects, causing recombination and degradation, limiting commercialization.

Purpose of the Study:

• To develop a halide exchange strategy using inert metal chlorides (MnCl2/ZnCl2) to improve Pb-Sn perovskite solar cells (PSCs).
• To reduce Sn4+ concentration and form an inorganic protective layer for enhanced stability and efficiency.

Main Methods:

• A halide exchange strategy using inert metal chlorides (MnCl2/ZnCl2) was employed.
• Metal chlorides reacted with SnI4 via ligand substitution, producing volatile SnCl4 and forming MnI2/ZnI2 passivation layers.
• Post-treatment induced partial dissolution-recrystallization to enlarge grain size and reduce stress.

Main Results:

• Reduced Sn4+ concentrations and formation of inorganic passivation layers at grain boundaries.
• Optimized energy-level alignment at the perovskite surface, improving carrier separation and extraction.
• Achieved a champion power conversion efficiency (PCE) of 23.06% with enhanced stability (90% PCE retention after 1000h).

Conclusions:

• Inert metal chloride post-treatment is a novel strategy for stabilizing Pb-Sn mixed perovskites.
• The method effectively reduces defects and improves device performance and longevity.
• Opens avenues for developing highly efficient and stable perovskite tandem solar cells.