Filling Chlorine Vacancy with Bromine: A Two-Step Hot-Injection Approach Achieving Defect-Free Hybrid Halogen...

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Mixed-halide perovskite nanocrystals (NCs) are promising for high-efficiency blue light-emitting diodes (LEDs).
• Conventional synthesis methods (one-step or post-synthetic anion exchange) lead to deep-level chlorine vacancy defects.
• These defects limit photoluminescence quantum yields (PLQYs) to below 30%.

Purpose of the Study:

• To develop a novel synthesis strategy for high-quality mixed-halide perovskite NCs.
• To overcome the limitations of existing methods in preventing chlorine vacancy defects.
• To achieve highly efficient and stable blue emission for LED applications.

Main Methods:

• A two-step hot-injection approach was optimized, controlling both thermodynamic and kinetic processes.
• Critical parameters, including the identity of bromine precursors and injection temperature, were investigated.
• This method enables simultaneous chlorine vacancy filling and efficient anion exchange.

Main Results:

• Defect-free CsPb(Cl/Br)3 NCs were synthesized with saturated blue emission at ~460 nm.
• Achieved near-unity PLQY and a narrow emission bandwidth of 18 nm.
• Fabricated LEDs demonstrated a low turn-on voltage (~4.0 V) and stable electroluminescence at 460 nm.

Conclusions:

• The two-step hot-injection method effectively suppresses defects in mixed-halide perovskites.
• This strategy yields highly efficient blue emitters with excellent optoelectronic properties.
• The findings offer new insights for designing high-quality chlorine-containing perovskites for optoelectronic devices.