Determining the Ion Mobility in Perovskite Solar Cells from Impedance Spectroscopy.

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Mobile ions in metal halide perovskites are a primary cause of perovskite solar cell (PSC) degradation.
• Accurate characterization of ion density and mobility is essential for improving the operational stability and longevity of PSCs.

Purpose of the Study:

• To introduce a novel, direct method for determining ion mobility in PSCs using impedance spectroscopy.
• To validate the proposed formula through comprehensive simulations and experimental verification.

Main Methods:

• Development of a new formula to calculate ion mobility directly from impedance spectroscopy data.
• Extensive drift-diffusion simulations were performed, varying 38 parameters to validate the formula across diverse PSC conditions.
• Experimental validation using a methylammonium lead iodide PSC.

Main Results:

• The proposed formula accurately determines ion mobility from the low-frequency features of the impedance spectrum.
• Simulations confirmed the formula's validity across a wide range of PSC parameters.
• Experimentally determined ion mobility for methylammonium lead iodide PSC was 4 × 10^-10 m² V^-1 s^-1.

Conclusions:

• The new impedance spectroscopy-based formula provides a precise and straightforward method for quantifying ion mobility in PSCs.
• This method is crucial for understanding and mitigating ion-related degradation mechanisms in perovskite solar cells.
• The findings pave the way for developing more stable and durable perovskite solar cell technologies.