Tunable Crystallization and Nucleation of Planar CH₃NH₃PbI₃ through Solvent-Modified Interdiffusion.

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Efficient planar perovskite solar cells require smooth, compact light-absorbing layers.
• Two-step deposition of methylammonium iodide (MAI) and lead iodide (PbI2) leads to inconsistent perovskite (CH3NH3PbI3) crystallization.
• Controlling nucleation and growth is crucial for film uniformity and device performance.

Purpose of the Study:

• To develop a facile solvent additive strategy for controlling perovskite crystallization kinetics.
• To improve the morphological properties and crystallite size distribution of perovskite thin films.
• To enhance the photovoltaic performance of planar perovskite solar cells.

Main Methods:

• Investigated the effects of various solvent additives (DMF, DMSO, GBL, CB, DEE) on MAI solutions.
• Utilized atomic force microscopy (AFM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) for morphological and structural analysis.
• Correlated thin film properties with photovoltaic performance of fabricated solar cell devices.

Main Results:

• Solvent additives successfully retarded perovskite crystallization and accelerated MAI diffusion.
• Achieved ultrasmooth perovskite thin films with narrow crystallite size variation.
• Demonstrated improved light absorption and band structure in the treated perovskite films.
• Observed enhanced photovoltaic performance in solar cells fabricated with these optimized films.

Conclusions:

• The solvent additive strategy offers a new pathway for fabricating highly efficient planar perovskite solar cells.
• Controlling perovskite nucleation and growth through solvent engineering is key to improving device performance.
• Ultrasmooth perovskite layers are critical for advancing perovskite solar cell technology.