Localized Lead-Chelating Insulator Bottom Contact for Efficient and Stable p-i-n Perovskite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Defective interfaces between perovskites and hole-transport layers (HTLs) hinder the efficiency of p-i-n perovskite solar cells (PSCs).
• Uncoordinated Pb2+ ions and pinholes at the interface contribute to performance limitations.

Purpose of the Study:

• To improve the performance and stability of PSCs by addressing bottom interface defects.
• To investigate the effect of an ultrathin poly (methyl methacrylate) (PMMA) layer on perovskite film quality and device efficiency.

Main Methods:

• Incorporation of an ultrathin PMMA layer onto PTAA HTLs.
• Characterization using transient reflection (TR) spectroscopy.
• Fabrication and testing of FA0.90Cs0.10PbI2.83Br0.17-based PSCs.

Main Results:

• PMMA filled pinholes and coordinated with Pb2+ ions, passivating the perovskite bottom surface.
• The PMMA layer did not impede charge transport at the PTAA/perovskite interface.
• PMMA induced preferred (111) facet orientation and reduced lattice strain in perovskites.
• PMMA's deep HOMO level suppressed I2 permeation and reactions with PTAA.
• Achieved a power conversion efficiency of 22.6% and significantly enhanced device stability.

Conclusions:

• Ultrathin PMMA is an effective interfacial layer for improving PSC performance and stability.
• PMMA passivates defects, promotes favorable crystal growth, and enhances interfacial energetics.
• The developed strategy offers a promising route for high-performance and durable perovskite solar cells.