Multidentate Chelation Modulates PbI₂ Crystallization and Buried-Interface Formation in Perovskite Solar Cells.

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• The buried interface is a critical bottleneck in two-step processed perovskite solar cells (PSCs).
• Incomplete conversion of lead iodide (PbI₂) and defect-induced nonradiative recombination limit device performance.
• Effective strategies are needed to engineer this buried interface for improved efficiency and stability.

Purpose of the Study:

• To develop a molecular engineering strategy to address the buried interface limitations in PSCs.
• To investigate the use of a multifunctional additive, PTAC-SH, for simultaneous PbI₂ template engineering and interface passivation.
• To enhance the power conversion efficiency (PCE) and operational stability of perovskite solar cells.

Main Methods:

• Employed pentaerythritol tetrakis(2-mercaptoacetate) (PTAC-SH) as a multifunctional additive.
• Utilized synergistic thiol and carbonyl coordination sites in PTAC-SH for multidentate chelation with Pb²⁺.
• Investigated PTAC-SH's role in directing porous PbI₂ scaffold formation and in situ interfacial defect passivation.

Main Results:

• PTAC-SH facilitated the formation of a porous PbI₂ scaffold, enabling efficient infiltration and conversion.
• PTAC-SH enriched at the buried interface, passivating defects and optimizing energy-level alignment.
• Devices achieved a champion PCE of 25.33% (FA_0.84MA_0.16PbI₃) and 26.07% (FA_0.98Cs_0.02PbI₃) with excellent stability (>95% PCE retention after 1700 h).

Conclusions:

• PTAC-SH is a highly effective additive for simultaneously engineering the PbI₂ template and optimizing the buried interface in PSCs.
• This structure-guided molecular design strategy significantly enhances perovskite film quality, interfacial properties, and device performance.
• The approach offers a promising pathway towards high-performance and stable perovskite solar cells.