Distinguishing Electron Diffusion and Extraction in Methylammonium Lead Iodide.

Area of Science:

• Materials Science
• Photovoltaics
• Spectroscopy

Background:

• Charge diffusion and extraction are critical for solar cell performance.
• Hybrid perovskite solar cells offer promising efficiency but require optimized charge transport.

Purpose of the Study:

• To investigate electron diffusion and transfer in hybrid perovskite films.
• To distinguish between diffusion and transfer processes and identify rate-limiting steps.
• To evaluate the impact of interlayers on charge extraction.

Main Methods:

• Utilizing time-resolved photoluminescence spectroscopy.
• Employing site-selective excitation from opposite sides of the sample.
• Analyzing electron diffusion and transfer dynamics in methylammonium lead iodide (MAPbI₃) films.

Main Results:

• Electron transfer velocity between MAPbI₃ and SnO₂ is significantly enhanced by a fullerene monolayer.
• Electron diffusion within the MAPbI₃ layer becomes the rate-limiting step for charge extraction.
• Site-selective excitation successfully separated diffusion and transfer processes.

Conclusions:

• Optimizing electron diffusion in MAPbI₃ is key to improving electron extraction efficiency.
• Fullerene interlayers can accelerate charge transfer, shifting the bottleneck to diffusion.
• This study provides insights for designing more efficient n-i-p type perovskite solar cells.