A‑Site-Dependent Oxidative Stability in Tin-Lead Halide Perovskites Reveals Kinetic Origins via Gradient Oxidation...

Area of Science:

• Materials Science
• Solid State Chemistry
• Photovoltaics

Background:

• Tin-lead (Sn-Pb) perovskites are key for low-bandgap solar cells.
• Sn²⁺ oxidation causes rapid degradation, limiting device longevity.
• A-site cation composition affects stability, but thermodynamic models are insufficient.

Purpose of the Study:

• Investigate the oxidation behavior of Sn-Pb perovskites with varied A-site compositions.
• Elucidate the role of surface reaction kinetics versus thermodynamics.
• Identify strategies for enhancing the stability of Sn-Pb perovskites.

Main Methods:

• In situ spectroscopic experiments.
• First-principles modeling.
• Analysis of A-site cation effects on oxidation and migration.

Main Results:

• Surface reaction kinetics, not just thermodynamics, govern Sn-Pb perovskite oxidation.
• Cesium-rich perovskites show higher activation energy barriers for Sn oxidation and vacancy migration.
• A dense SnO_x surface layer passivates Cs-rich perovskites, preventing bulk oxidation.
• Organic cation-based perovskites exhibit more uniform bulk oxidation.

Conclusions:

• Kinetics and A-site engineering are crucial for Sn-Pb perovskite stability.
• Composition-dependent gradient oxidation is a key mechanism.
• Findings offer insights beyond traditional thermodynamic analyses for optoelectronic applications.