Dual Additives toward High-Performance Wide-Bandgap Perovskite Solar Cells.

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Wide-bandgap (WBG) perovskites are crucial for high-efficiency tandem solar cells.
• Their performance is limited by voltage loss, instability, and defects due to Br-rich compositions.
• Iodine redox imbalance and undercoordinated Pb2+ sites exacerbate nonradiative recombination and ion migration.

Purpose of the Study:

• To develop a strategy for optimizing WBG perovskite solar cells for tandem applications.
• To address the limitations of voltage loss and instability in WBG perovskites.
• To improve the quality and stability of WBG perovskite films.

Main Methods:

• A dual-additive strategy using cesium formate (CsFa) and formamidinium formate (FAFa).
• Utilizing formate ions (HCOO-) as a reducing agent and coordinating ligand.
• Investigating the effects of formate on iodine redox chemistry, Pb2+ coordination, and film crystallization.

Main Results:

• Formate ions rebalanced iodine redox chemistry and coordinated with Pb2+ sites.
• Improved perovskite film quality with enlarged grain size and reduced defect density.
• Achieved 17.83% power conversion efficiency in P-I-N perovskite solar cells with a ~1.79 eV bandgap.

Conclusions:

• The dual-additive strategy effectively optimizes WBG perovskite performance for tandem solar cells.
• This approach enhances operational stability and addresses key degradation pathways.
• Demonstrates a viable method for improving WBG top cells in photovoltaic devices.