Halide anions engineered ionic liquids passivation layer for highly stable inverted perovskite solar cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Long-term stability is a critical challenge for metal halide perovskite solar cells (PSCs).
• Ionic liquids (ILs) offer a promising approach to enhance PSC stability.
• Controlling halide anions in ILs and their effect on perovskite films needs further investigation.

Purpose of the Study:

• To investigate the impact of different halide anions in 1-ethyl-3-methylimidazolium (EMIMX) ionic liquids on inverted PSC performance and stability.
• To explore the formation of passivation layers and their influence on perovskite film morphology and defect suppression.

Main Methods:

• In situ growth technique using EMIMX (X = Cl, Br, I) ionic liquids in inverted PSCs.
• Surface morphology analysis of perovskite films.
• Performance and long-term stability testing under various environmental conditions (ambient air, humidity, elevated temperature).

Main Results:

• EMIMX formed a 1D passivation layer, improving perovskite film morphology.
• Suppression of surface defects and non-radiative energy losses, leading to enhanced hydrophobic properties.
• EMIMBr-modified PSCs achieved a power conversion efficiency (PCE) of 20.0% (vs. 18.06% for control).
• Unencapsulated devices retained >90% PCE after 3000 hours in ambient air.

Conclusions:

• Ionic liquids with tailored halide anions can effectively passivate perovskite surfaces and improve device stability.
• EMIMBr demonstrates significant potential for developing highly stable and efficient inverted PSCs.
• The developed devices exhibit excellent long-term durability under ambient conditions and resilience to harsh environments.