Rationally Designed Self-Assembled Monolayer for Dual-Site Passivation Enables Efficient and Stable Perovskite Solar...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Self-assembled monolayers (SAMs) are crucial hole transport layers in perovskite solar cells (PSCs).
• Molecular aggregation and weak interfacial interactions in SAMs limit PSC power conversion efficiency (PCE) and stability.
• Existing SAMs face challenges like imperfect surface coverage and energy losses at the interface.

Purpose of the Study:

• To develop a site-specific halogenation strategy to enhance SAM-perovskite interactions.
• To improve the dispersibility and interfacial properties of carbazole-based SAMs.
• To boost the PCE and operational stability of inverted PSCs through molecular engineering.

Main Methods:

• Synthesized three dichlorinated positional isomers of (4-(3,6-diphenyl-9H-carbazol-9-yl) butyl) phosphonic acid (Ph-4PACz).
• Introduced chlorine atoms at specific positions on the phenyl ring to tune molecular dipole and spatial configuration.
• Investigated the effect of halogenation on molecular aggregation, SAM-perovskite coordination, and perovskite film quality.

Main Results:

• p-Cl-Ph-4PACz demonstrated ideal spatial matching for dual-site coordination with perovskite.
• Achieved suppressed molecular aggregation, reduced interfacial defects, and minimized nonradiative recombination.
• Inverted PSCs with p-Cl-Ph-4PACz reached a certified PCE of 26.13% and maintained 95.9% efficiency after 1000 hours.

Conclusions:

• Rational site-specific halogenation is an effective strategy to strengthen SAM-perovskite interfaces.
• The p-Cl-Ph-4PACz derivative significantly enhances both the efficiency and stability of inverted PSCs.
• This approach offers a promising pathway for advancing perovskite solar cell technology.