Dual-Ion Synergy Breaks 20% Barrier in Electron Transport Layer-Free Perovskite Solar Modules

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Electron transport layer-free (ETL-free) perovskite solar cells (PSCs) offer simplified architecture for industrial deployment.
• High efficiency in ETL-free PSCs often necessitates complex intermediate layers, contradicting the simplified design goal.

Purpose of the Study:

• To enhance the efficiency and stability of ETL-free PSCs through a simplified passivation strategy.
• To investigate the passivation mechanism of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) on perovskite films.

Main Methods:

• Passivation of perovskite films using EMIMTFSI.
• Analysis of EMIMTFSI interactions with perovskite components (lead and iodide ions).
• Characterization of perovskite film properties (crystallization, energy levels, defects).
• Fabrication and testing of ETL-free PSC devices and modules.

Main Results:

• EMIMTFSI passivation enhances perovskite crystallization, improves energy level alignment, and reduces defects.
• EMIM⁺ and TFSI^- species interact with perovskite ions, with TFSI^- forming hydrogen bonds.
• Achieved a certified power conversion efficiency of 22.08% for ETL-free PSCs.
• Reported the first ETL-free perovskite solar module with 20.27% efficiency and excellent stability.

Conclusions:

• EMIMTFSI passivation offers a simplified and effective approach to boost ETL-free PSC performance.
• The synergistic interactions within EMIMTFSI contribute to superior device characteristics.
• This method paves the way for cost-effective commercialization of perovskite photovoltaics.