In-Situ Formed Type I Nanocrystalline Perovskite Film for Highly Efficient Light-Emitting Diode

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Organic-inorganic halide perovskites offer excellent color purity and tunable band gaps for light-emitting diodes (LEDs).
• Perovskite nanocrystals exhibit high photoluminescence quantum yield (>90%), but this significantly drops (<20%) in thin films, hindering LED efficiency.
• Low photoluminescence quantum yield in perovskite thin films is a major obstacle for developing efficient perovskite LEDs.

Purpose of the Study:

• To develop a method for creating highly luminescent methylammonium lead bromide (MAPbBr₃) nanocrystal thin films in situ.
• To overcome the challenge of reduced photoluminescence quantum yield in perovskite thin films for enhanced LED performance.
• To demonstrate a highly efficient green LED based on the developed nanocrystalline thin film.

Main Methods:

• Utilized nonstoichiometric adduct formation with excess MABr (CH₃NH₃Br) relative to PbBr₂ in the precursor solution.
• Employed a solvent-vacuum drying process to preserve the formed nanocrystals within the thin film.
• Investigated the role of excess MABr in inhibiting crystal growth and creating type I band alignment.

Main Results:

• Successfully formed highly luminescent MAPbBr₃ nanocrystals within the thin film.
• Achieved a fast photoluminescence lifetime of 3.9 ns with negligible trapping processes.
• Fabricated a green LED with a maximum external quantum efficiency of 8.21% and a current efficiency of 34.46 cd/A.

Conclusions:

• The developed method effectively produces highly luminescent MAPbBr₃ nanocrystal thin films.
• The strategy overcomes the photoluminescence quenching issue in perovskite thin films.
• This work paves the way for highly efficient perovskite-based optoelectronic devices, particularly LEDs.