Brightly Luminescent and Color-Tunable Colloidal CH₃NH₃PbX₃ (X = Br, I, Cl) Quantum Dots: Potential Alternatives for Display Technology

TLDR

Organometal halide perovskites are inexpensive, color‑tunable, narrow‑band emitters, yet they exhibit low photoluminescence quantum yields at low excitation fluencies, and colloidal CH3NH3PbX3 quantum dots are expected to show interesting nanoscale excitonic properties with potential applications in lasers, electroluminescence devices, and optical sensors. The study aims to develop a ligand‑assisted reprecipitation method to fabricate brightly luminescent, color‑tunable CH3NH3PbX3 (X = Br, I, Cl) quantum dots achieving up to 70 % absolute quantum yield at room temperature and low excitation fluencies. The authors employed ligand‑assisted reprecipitation to synthesize the quantum dots, followed by comprehensive composition and surface characterizations and time‑ and temperature‑dependent photoluminescence spectroscopy to elucidate the PL enhancements. Size reduction to ~3.3 nm increases exciton binding energy and, with proper Br‑rich surface passivation, boosts PL quantum yield, while the resulting green‑emissive QDs combined with red K2SiF6:Mn4+ color converters enable wide‑color‑gamut white‑light LEDs with superior color quality.

Abstract

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2–8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn4+ as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.