Tailoring Precursor-Solvent Coordination Controls the Crystallization Kinetics and Nuclei Growth for Phase...

Area of Science:

• Materials Science
• Photovoltaics
• Crystallization Engineering

Background:

• Wide-bandgap (WBG) perovskites are crucial for high-efficiency tandem solar cells.
• Unbalanced nucleation-growth in WBG perovskites leads to defects and phase segregation.
• The role of volatile ammonium chloride (AC) in WBG perovskite crystallization is largely unexplored.

Purpose of the Study:

• To investigate the effect of volatile ammonium chloride (AC) on WBG perovskite precursor chemistry and crystallization.
• To understand how AC influences nucleation-growth kinetics and film quality.
• To assess the impact of AC treatment on the performance and stability of WBG perovskite solar cells.

Main Methods:

• In situ characterizations to monitor crystallization processes.
• Analysis of precursor-solvent coordination.
• Crystallization kinetics and phase transformation studies.
• Fabrication and characterization of WBG perovskite solar cells.

Main Results:

• AC weakens precursor-solvent coordination and destabilizes hexagonal polytypes.
• AC induces specific solvated iodoplumbate complexes, balancing nucleation-growth.
• Cl-rich intermediates and cation exchange with NH4+, Cs+, and FA+ ions control crystal growth.
• Suppression of undesired phases, promotion of cubic perovskite formation, and defect self-elimination were observed.
• AC-treated films yielded 1.73 eV WBG perovskite solar cells with 18% PCE and 1.22 V V_oc.

Conclusions:

• AC effectively controls WBG perovskite crystallization by modifying precursor chemistry and kinetics.
• The treatment leads to higher quality perovskite films with suppressed defects and improved phase purity.
• AC-treated WBG perovskite solar cells exhibit enhanced power conversion efficiency and photostability.