Halide-Cation Interactions Enable Controlled Crystallization and Defect Minimization in High-Performance...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Wide-bandgap (WBG) perovskites are crucial for high-efficiency solar cells.
• Improving the stability and performance of WBG perovskites remains a key challenge.
• All-perovskite tandem solar cells (TSCs) offer a promising route to exceed the Shockley-Queisser limit.

Purpose of the Study:

• To investigate the synergistic passivation effects of Cl-salt and F-salt on WBG perovskite subcells and TSCs.
• To elucidate the underlying mechanisms responsible for performance enhancement.
• To assess the long-term operational stability of the treated devices.

Main Methods:

• Synergistic passivation treatment using potassium hexafluorophosphate (KPF6) derived salts (Cl-salt and F-salt).
• Fabrication and characterization of WBG perovskite subcells and all-perovskite TSCs.
• Performance evaluation including power conversion efficiency (PCE), open-circuit voltage (VOC), and fill factor (FF).
• Stability testing under continuous illumination (1 sun) for 700 hours.

Main Results:

• WBG subcells treated with Cl-salt and F-salt achieved PCEs of 20.5% and 20.3%, respectively.
• Significant enhancements in open-circuit voltage (VOC) and fill factor (FF) were observed.
• All-perovskite TSCs incorporating the treated WBG subcells reached PCEs of 29.2% (Cl-salt) and 29.3% (F-salt).
• The treated devices demonstrated excellent operational stability, retaining 87% of their initial PCE after 700 hours of MPP tracking.

Conclusions:

• Synergistic passivation with Cl-salt or F-salt is an effective strategy to enhance WBG perovskite solar cells and TSCs.
• Dual mechanisms involving PF6- coordination and hydrogen bonding contribute to improved film quality and suppressed phase segregation.
• The developed passivation approach offers a viable pathway towards highly efficient and stable perovskite-based photovoltaic devices.