Conjugated Oligoelectrolyte-Driven Self-Assembled Monolayer for Bidirectional Interfacial Engineering in Sn-Pb...

Area of Science:

• Materials Science
• Energy Science
• Chemistry

Background:

• Tin-lead (Sn-Pb) perovskites offer ideal bandgaps for efficient solar cells but face challenges with interfacial instability, including Sn vacancies, oxidation, and poor film quality.
• Conventional self-assembled monolayers (SAMs) used as hole-selective interlayers exhibit weak binding and poor wettability, hindering scalable perovskite solar cell (PSC) performance.

Purpose of the Study:

• To develop a novel SAM with enhanced interfacial properties for improved tin-lead perovskite solar cell (PSC) performance and stability.
• To investigate the molecular design of SAMs for better interfacial coverage, defect suppression, and Sn2+ oxidation prevention in PSCs.

Main Methods:

• Design and synthesis of a conjugated oligoelectrolyte SAM (4PACz-TMABr) featuring dual phosphonic acid groups and quaternary ammonium bromide ionic moieties.
• Characterization of interfacial properties using techniques like density functional theory (DFT) calculations.
• Fabrication and performance testing of tin-lead perovskite solar cells (PSCs) with the novel SAM.

Main Results:

• The 4PACz-TMABr SAM demonstrated improved interfacial coverage on indium tin oxide and effectively suppressed perovskite defects and Sn2+ oxidation.
• DFT calculations supported the formation of uniform, high-crystallinity Sn-Pb perovskite films.
• Small-area devices achieved a champion power conversion efficiency of 22.67%, while 1 cm2 devices reached 17.61%, with enhanced thermal stability.

Conclusions:

• The rationally designed 4PACz-TMABr SAM provides a strategic molecular approach to overcome interfacial instability in Sn-Pb PSCs.
• This SAM facilitates orderly alignment and acts as a bidirectional linker, promoting efficient charge transfer and device stability.
• The findings pave the way for developing scalable, stable, and high-efficiency Sn-Pb perovskite solar cells.