Interfacial Energy-Level Engineering with Diammonium Halide for Efficient and Stable Perovskite Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Surface Chemistry

Background:

• Efficient charge extraction and reduced recombination are crucial for high-performance perovskite solar cells (PSCs).
• Interfacial energy-level alignment plays a key role in PSC performance, but the influence of halide substituents in diamine ligands remains unclear.

Purpose of the Study:

• To investigate how halide substituents (Cl, Br, I) in diamine ligands (C6-DAX2) affect the surface electronic structure of perovskite films.
• To understand the role of these ligands in modulating interfacial energy-level alignment for improved charge transport in PSCs.

Main Methods:

• Synthesis and application of halide-substituted diamine ligands (C6-DAX2) on perovskite films.
• Characterization of surface electronic structure, including work function and Fermi level.
• Fabrication and testing of inverted PSCs incorporating the modified perovskite films.

Main Results:

• Stepwise halide substitution (Cl to Br to I) progressively decreased the work function and shifted the Fermi level upward.
• This modulation reduced the conduction band offset with the C60 electron transport layer, facilitating electron transport.
• Inverted PSCs with C6-DAI2 achieved a champion power conversion efficiency of 25.0% and demonstrated excellent operational stability (85% retention after 1100 h).

Conclusions:

• Halide-substituted diamine ligands effectively tune the interfacial energy-level alignment in PSCs.
• Optimized interfacial properties lead to enhanced electron transport and suppressed recombination.
• The C6-DAI2 ligand shows significant promise for developing highly efficient and stable perovskite solar cells.