High-Efficiency Polycrystalline Perovskite Light-Emitting Diodes Based on Mixed Cations

Area of Science:

• Materials Science
• Optoelectronics
• Solid-State Chemistry

Background:

• Perovskite light-emitting diodes (PeLEDs) offer promising optoelectronic applications.
• Tuning chemical composition is crucial for optimizing PeLED performance and stability.
• Formamidinium (FA) and cesium (Cs) mixed cations are explored for enhanced properties.

Purpose of the Study:

• To investigate the impact of formamidinium (FA) and cesium (Cs) cation mixing on polycrystalline perovskite films.
• To understand the relationship between chemical composition, film properties, and device performance in PeLEDs.
• To achieve high-efficiency and stable FA-Cs-based PeLEDs without quantum dot synthesis.

Main Methods:

• Fabrication of uniform single-phase FA_1-xCs_xPbBr₃ polycrystalline films via one-step formation with varying FA:Cs molar ratios.
• Systematic investigation of film morphology, crystal structure, photoluminescence (PL), and electroluminescence (EL) properties.
• Characterization of the effects of Cs incorporation on grain size, trap density, PL quantum efficiency (PLQE), PL lifetime, and photostability.

Main Results:

• Incorporation of Cs⁺ cations in FAPbBr₃ reduced grain size and trap density, leading to increased PLQE, PL lifetime, and current efficiency (CE).
• An optimal FA:Cs ratio (90:10) yielded the highest CE of 14.5 cd A^-1 with a narrow EL spectral width (21-24 nm).
• Increased Cs content beyond 10 mol % decreased crystallinity, purity, and luminescent properties, while Cs incorporation enhanced photostability.

Conclusions:

• Cs incorporation significantly influences the chemical, structural, and luminescent properties of FAPbBr₃ polycrystalline films.
• A breakthrough in achieving high-efficiency FA_1-xCs_xPbBr₃ PeLEDs is demonstrated through optimized cation mixing.
• The study provides valuable insights for designing efficient and stable perovskite optoelectronic devices.