Stabilizing Metal Oxide Free n-i-p Perovskite Solar Cells by Electron-Transporting, Strong-Dipole Self-Assembled...

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Metal oxides are common electron-transporting layers in perovskite solar cells (PSCs).
• Their limitations hinder device performance and longevity.
• Developing alternatives is crucial for advancing PSC technology.

Purpose of the Study:

• To introduce 3-cyanopropionic acid (CPA) as a novel electron-transporting layer alternative to metal oxides in n-i-p PSCs.
• To investigate the mechanism by which CPA enhances device efficiency and stability.
• To achieve high power conversion efficiency (PCE) and improved operational lifetime.

Main Methods:

• Utilized 3-cyanopropionic acid (CPA), a self-assembled molecule (SAM), as an interfacial layer.
• Anchored CPA to fluorine-doped tin oxide (FTO) substrates via covalent bonding through its carboxyl group.
• Leveraged the cyano group for vertical molecular assembly, creating an interfacial dipole.
• Investigated CPA's effect on perovskite crystallization, lattice strain, and interfacial contact.

Main Results:

• Achieved a champion power conversion efficiency (PCE) of 25.17% in n-i-p PSCs, a record for metal-oxide-free devices.
• Demonstrated enhanced electron extraction due to favorable energy-level alignment facilitated by the interfacial dipole.
• Observed improved perovskite film quality, reduced lattice strain, and better interfacial contact.
• Unencapsulated devices retained ~90% of initial PCE after 2500 hours of storage.

Conclusions:

• 3-Cyanopropionic acid (CPA) effectively replaces traditional metal oxides as an electron-transporting layer in PSCs.
• CPA significantly enhances both the power conversion efficiency and long-term stability of perovskite solar cells.
• This work presents a promising strategy for developing highly efficient and stable metal-oxide-free perovskite solar cells.