Differentiating the 2D Passivation from Amorphous Passivation in Perovskite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Two-dimensional (2D) perovskite layers enhance three-dimensional (3D) perovskite solar cell (PSC) performance and stability.
• Spacer cation effects and 2D capping layer quality are critical for device optimization.
• Engineering 3D/2D perovskite heterojunctions is key to advancing PSC technology.

Purpose of the Study:

• To compare the impact of two fluorinated benzamidine salts on 3D/2D perovskite film formation and PSC performance.
• To investigate the role of intramolecular charge polarization and hydrogen bonding in forming crystalline 2D perovskite layers.
• To evaluate the efficiency and stability enhancements offered by different 2D capping strategies in PSCs.

Main Methods:

• Synthesis and characterization of 3D/2D perovskite films using 4-(trifluoromethyl) benzamidine hydrochloride (4TF-BA·HCl) and 4-fluorobenzamidine hydrochloride (4F-BA·HCl).
• Fabrication and testing of PSC devices incorporating the engineered perovskite films.
• Analysis of film morphology, electronic properties, and device performance under various storage conditions.

Main Results:

• 4F-BA·HCl formed a high-performance crystalline 2D perovskite heterojunction, leading to efficiencies exceeding 25%.
• 4TF-BA·HCl resulted in an amorphous layer but improved device efficiency to 24% due to benzamidine passivation.
• Devices based on 4F-BA exhibited superior longevity and stability compared to 4TF-BA and control devices.

Conclusions:

• Balanced intramolecular charge polarization and hydrogen bonding, as seen with 4F-BA, are crucial for forming effective crystalline 2D perovskite layers.
• Benzamidine derivatives offer valuable passivation effects, enhancing PSC efficiency even with amorphous capping layers.
• 4F-BA represents a promising strategy for developing highly efficient and stable perovskite solar cells.