High-Efficiency Perovskite Solar Cells with Improved Interfacial Charge Extraction by Bridging Molecules

Area of Science:

• Materials Science
• Photovoltaics
• Nanotechnology

Background:

• The performance and stability of perovskite solar cells (PSCs) are significantly influenced by the interface between the perovskite layer and the electron transporting layer (ETL).
• Interface heterogeneity can negatively impact carrier dynamics and device efficiency.

Purpose of the Study:

• To enhance the SnO₂/perovskite interface in n-i-p PSCs using a bridging molecule.
• To improve carrier dynamics, crystallinity, and stability of PSCs.

Main Methods:

• Modification of the SnO₂/perovskite interface with (2-aminoethyl)phosphonic acid (AEP).
• Characterization of surface properties, perovskite film quality, and carrier dynamics using techniques including femtosecond transient reflection (fs-TR) spectroscopy.
• Fabrication and testing of PSC devices.

Main Results:

• AEP effectively passivated surface traps and leakage current on the SnO₂ surface, leading to a more uniform surface potential.
• AEP promoted enhanced perovskite film growth with higher crystallinity, phase purity, and reduced defects.
• Facilitated charge extraction at the interface resulted in a champion power conversion efficiency (PCE) of 26.40% (certified 25.98%).
• Improved interface integrity led to enhanced operational durability of approximately 1400 hours for unencapsulated PSCs.

Conclusions:

• The introduction of AEP as a bridging molecule is a viable strategy for optimizing the SnO₂/perovskite interface in PSCs.
• This interfacial engineering significantly boosts both the efficiency and long-term stability of perovskite solar cells.