Imidazole-Based Ionic Liquid Engineering for Perovskite Solar Cells with High Efficiency and Excellent Stability

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Chemistry

Background:

• Perovskite solar cells (PSCs) show great promise but are limited by inherent defects affecting efficiency and stability.
• Defects in perovskite materials lead to charge recombination and degradation, hindering commercial viability.
• Ion migration within perovskite layers is a key factor contributing to device instability.

Purpose of the Study:

• To introduce a novel additive, 1-benzyl-3-methylimidazolium bromide (BzMIMBr), for defect passivation and stability enhancement in PSCs.
• To investigate the mechanism by which BzMIMBr reduces bulk defects and suppresses ion migration.
• To improve the power conversion efficiency (PCE) and long-term operational stability of inverted PSCs.

Main Methods:

• Incorporation of BzMIMBr into perovskite precursor solutions for inverted PSC fabrication.
• Passivation of uncoordinated Pb2+ cations via electron-rich nitrogen in BzMIMBr.
• Investigation of BzMIMBr's effect on perovskite crystallization kinetics and film morphology.
• Characterization of film properties, including surface uniformity, defect density, and carrier recombination.
• Performance testing of PSCs under ambient conditions and long-term stability assessment.

Main Results:

• BzMIMBr effectively passivates Pb2+ defects and hinders ion migration by interacting with perovskite components.
• Improved perovskite film quality with enhanced morphology, surface uniformity, and crystallinity.
• Reduced trap states and nonradiative carrier recombination, leading to higher PCE.
• BzMIMBr-doped PSCs achieved a PCE of 23.37%, compared to 20.71% for pristine devices.
• Unencapsulated devices maintained 93% of initial efficiency after 1800 hours in 45% relative humidity, demonstrating enhanced stability and hydrophobicity.

Conclusions:

• 1-benzyl-3-methylimidazolium bromide (BzMIMBr) is a highly effective additive for improving perovskite solar cell performance and stability.
• BzMIMBr acts as a multifunctional passivating agent, reducing defects and suppressing ion migration.
• The enhanced hydrophobicity and stability of BzMIMBr-doped PSCs offer a pathway towards more durable and efficient solar energy conversion.