In Situ Pseudo-Halide Diffusion Enables Buried Interface Regulation and Crystallinity Enhancement in Perovskite Solar...

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Chemistry

Background:

• Regulating buried interfaces is crucial for high-quality perovskite films in solar cells.
• Interfacial defects and poor crystallization limit perovskite solar cell performance and stability.

Purpose of the Study:

• To develop a thermally activated buried interface strategy using lithium formate (LiHCOO) for perovskite solar cells.
• To investigate the mechanism of in situ pseudo-halide diffusion for interface reconstruction and defect passivation.

Main Methods:

• Utilizing a thermally activated lithium formate (LiHCOO) buried interface strategy.
• Inducing pseudo-halide diffusion through high-temperature treatment of LiHCOO polymorphs.
• Analyzing the effects of diffused HCOO- on perovskite crystallization, defect compensation, and strain release.
• Passivating the SnO2 surface to improve interfacial electrical properties and energy level alignment.

Main Results:

• LiHCOO transforms to a metastable monoclinic phase, enabling deeper HCOO- diffusion.
• Diffused HCOO- passivates undercoordinated Pb2+ sites, inhibits pinholes, reduces trap density, and compensates halide vacancies.
• SnO2 surface passivation reduces oxygen vacancies and hydroxyl defects, enhancing built-in potential from 0.91 to 1.00 V.
• Achieved a champion perovskite solar cell efficiency of 25.48% with improved open-circuit voltage (1.213 V) and fill factor (82.57%).

Conclusions:

• Polymorph-mediated pseudo-halide diffusion is a novel approach for low-loss perovskite photovoltaics.
• The LiHCOO strategy effectively reconstructs the buried interface, enhancing device performance and long-term stability.
• This method offers a pathway towards robust and efficient perovskite solar cells.