A self-assembled molecule directs ordered α-FAPbI₃ for n-i-p perovskite solar cells

Area of Science:

• Materials Science
• Renewable Energy
• Crystallography

Background:

• Formamidinium lead iodide (FAPbI3) perovskite is crucial for high-efficiency solar cells but suffers from unstable α-phase crystallization.
• Existing methods often require incompatible polar protic solvents, limiting their application with perovskite surfaces.

Purpose of the Study:

• To develop a novel strategy for directing the ordered crystallization of α-FAPbI3 in n-i-p solar cells.
• To overcome the kinetic instability hindering the application of FAPbI3 perovskites.
• To improve the power conversion efficiency (PCE) and stability of perovskite solar cells.

Main Methods:

• Incorporation of a self-assembled molecule (SAM) from non-polar, aprotic solvents into the anti-solvent during perovskite film formation.
• Utilizing an in-situ formed self-assembled layer as a dynamic template for top-down crystallization.
• Employing in-situ measurements to monitor crystallization dynamics, phase transitions, and crystal growth.

Main Results:

• The -SCN SAM strategy successfully directed ordered α-FAPbI3 crystallization in an n-i-p architecture.
• The SAM treatment suppressed intermediate phases, accelerated the δ-to-α transition, and slowed crystal growth, yielding highly ordered films.
• Achieved a champion PCE of 26.18% for single-junction devices and 21.70% for mini-modules.

Conclusions:

• Directed self-assembly using compatible SAMs is a powerful strategy for fabricating high-quality, stable α-FAPbI3 perovskite films.
• This approach significantly enhances the performance of n-i-p perovskite solar cells.
• The findings offer a promising route for the commercialization of efficient and stable perovskite solar technology.