Memory Seeds Enable High Structural Phase Purity in 2D Perovskite Films for High-Efficiency Devices

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Two-dimensional (2D) perovskites are promising for efficient and durable optoelectronic devices.
• Challenges include polydispersity in layer thickness and poor film formation, hindering device performance and stability.

Purpose of the Study:

• To develop a simple, scalable method for fabricating 2D perovskite thin films with homogenous layer thickness (phase purity).
• To investigate the film formation mechanism and its impact on device characteristics.

Main Methods:

• A "phase-selective method" involving dissolution of single-crystalline 2D perovskite powders.
• In situ characterizations to observe seed formation and crystal growth in solution.
• Fabrication of p-i-n photovoltaic devices using the prepared thin films.

Main Results:

• The phase-selective method yields 2D perovskite films with homogenous layer thickness.
• Sub-micrometer seeds in solution preserve crystal memory, dictating uniform grain growth.
• Fabricated photovoltaic devices achieved 17.1% efficiency with a 1.20 V open-circuit voltage.
• Devices maintained 97.5% of peak performance after 800 hours of illumination.

Conclusions:

• The phase-selective method enables the fabrication of high-quality, phase-pure 2D perovskite thin films.
• Homogenous layer thickness is crucial for enhancing photovoltaic device efficiency and stability.
• This approach offers a scalable pathway for advanced 2D perovskite optoelectronics.