Retarding solid-state reactions enable efficient and stable all-inorganic perovskite solar cells and modules

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Chemistry

Background:

• All-inorganic CsPbI3 perovskite solar cells (PSCs) show promise for tandem applications with efficiencies over 20%.
• Key challenges include inhomogeneous synthesis and poor stability of the CsPbI3 black phase, hindering large-scale production.

Purpose of the Study:

• To develop a method for preparing high-quality, large-area CsPbI3 films in air for improved PSCs.
• To address the stability issues of the CsPbI3 black phase during synthesis and operation.

Main Methods:

• Utilized a thermally stable ionic liquid, bis(triphenylphosphine)iminium bis(trifluoromethylsulfonyl)imide ([PPN][TFSI]), to control the solid-state reaction between Cs4PbI6 and dimethylammonium (DMA)PbI3.
• Investigated the role of [PPN][TFSI] in enhancing the formation energy of superficial vacancies and preventing phase degradation through Pb-O contacts.

Main Results:

• Successfully prepared high-quality, large-area CsPbI3 films in air using [PPN][TFSI].
• Achieved a certified power conversion efficiency (PCE) of 19.69% for PSCs, with a device PCE of 20.64%.
• Demonstrated long-term operational stability exceeding 1000 hours and a record 16.89% efficiency for a 28.17 cm2 all-inorganic perovskite solar module.

Conclusions:

• The ionic liquid [PPN][TFSI] effectively retards the solid-state reaction, enabling scalable fabrication of stable CsPbI3 films.
• [PPN][TFSI] enhances CsPbI3 stability by increasing vacancy formation energy, crucial for device longevity.
• This approach paves the way for efficient and stable all-inorganic PSCs and modules for large-scale solar energy conversion.