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Liquid-Liquid Interface-Based Thiocyanate Surface Treatment for Bright and Stable CsPbBr3 Nanocrystals
Rachel Lifer1, Nathan Rafisiman1,2, Saar Shaek1
1Department of Materials Science and Engineering, Technion - Israel Institute of Technology, 32000 Haifa, Israel.
Chemistry of Materials : a Publication of the American Chemical Society
|June 16, 2025
Summary
This study introduces a novel urea-ammonium thiocyanate ionic liquid for treating perovskite nanocrystals, significantly boosting their efficiency and stability by passivating surface defects. The method enhances photoluminescence quantum yield and prevents degradation, advancing perovskite device development.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Chemistry
Background:
- Lead halide perovskite devices require enhanced efficiency and stability for practical application.
- Previous thiocyanate treatments improved CsPbBr3 nanocrystal performance but lacked mechanistic clarity.
- Low thiocyanate solubility in nonpolar solvents hindered previous approaches.
Purpose of the Study:
- To develop a novel surface treatment for lead halide perovskite nanocrystals using a urea-ammonium thiocyanate ionic liquid.
- To elucidate the mechanism behind thiocyanate-induced improvements in perovskite nanocrystal efficiency and stability.
- To address the challenge of low thiocyanate solubility in traditional solvents.
Main Methods:
- Surface treatment of CsPbBr3 nanocrystals with a urea-ammonium thiocyanate (UAT)-based ionic liquid.
- Utilizing transmission electron microscopy (TEM) for atomic resolution imaging and surface analysis.
- Investigating structural and chemical changes on the nanocrystal surface.
Main Results:
- Achieved near-unity photoluminescence quantum yield (PLQY) and enhanced stability of perovskite nanocrystals.
- Atomic resolution TEM revealed sulfur enrichment and a 3% lattice dilation on treated surfaces.
- Demonstrated that thiocyanate binds to Pb cations, acting as a pseudohalide and passivating bromide vacancies.
Conclusions:
- The primary mechanism for performance enhancement is the passivation of surface traps associated with bromide vacancies.
- The UAT ionic liquid treatment effectively prevents NC degradation and enhances stability against ionic substitution.
- This method offers a significant advancement for perovskite-based devices by slowing ion migration.
