Overcoming Microstructural Defects at the Buried Interface of Formamidinium-Based Perovskite Solar Cells.

Area of Science:

• Materials Science
• Renewable Energy
• Device Physics

Background:

• Formamidinium (FA)-based perovskite photovoltaics (PVs) have shown great promise, but void formation at the perovskite-interlayer interface hinders performance.
• Existing strategies to mitigate voids are limited to specific perovskite-hole transport layer (HTL) combinations, lacking universal applicability.

Purpose of the Study:

• To develop a universal strategy to prevent void formation at the buried perovskite-HTL interface in p-i-n perovskite PVs.
• To investigate the impact of a novel film treatment on microstructural defects and device performance.

Main Methods:

• A sequential deposition method introducing methylammonium chloride (MACl) as a film treatment.
• Device photoluminescence (PL) measurements and conductive atomic force microscopy (c-AFM) to analyze microstructural defects.
• Steady-state and transient PL spectroscopy to assess charge carrier dynamics.

Main Results:

• The MACl treatment effectively eliminates voids at the perovskite-HTL interface, regardless of HTL type or perovskite thickness.
• Voids were found to impede charge extraction, reducing the device's short-circuit current.
• MACl treatment led to reduced defect states, suppressed nonradiative recombination, and extended carrier lifetimes up to 2.3 μs.
• The treatment broadened the processing window for perovskite fabrication, offering greater flexibility.

Conclusions:

• The MACl film treatment presents a universal and effective method for preventing detrimental void formation in perovskite PVs.
• This approach significantly enhances device performance by improving charge extraction and reducing recombination.
• The developed technique offers practical advantages for scalable perovskite solar cell fabrication.