Quantum-confinement effect on the linewidth broadening of metal halide perovskite-based quantum dots

Abstract

The linewidth broadening caused by various physicochemical effects does limit the well-known advantage of ultrahigh color purity of metal halide perovskites (MHPs) for use in next-generation light-emitting diodes (LEDs). We have theoretically examined the quantum- and dielectric-confinement effects of a quantum dot (QD) on the degree of photoluminescence linewidth broadening. It is predicted that the linewidth (Δλ QC) is mainly contributed by the two opposing effects: (i) the linewidth broadening due to the repulsive kinetic energy of confined excitons () and (ii) the overall linewidth narrowing caused by the attractive Coulomb interaction (). It is shown that the relative contribution essentially remains at a constant value and is evaluated as , which is independent of the QD size and the chemical nature of semiconducting emitter. We have computed Δλ QC for various QD sizes of the prototypical MHP emitter, MAPbBr3, where MA denotes a methylammonium (CH3NH3) organic cation. The calculated results show that the linewidth broadening due to the quantum confinement (Δλ QC) increases rapidly beginning at the QD radius approximately equal to 6.5 nm but Δλ QC is less than 2 nm even at R = 1.5 nm. Thus, Δλ QC is much narrower than the linewidth caused by the exciton-LO phonon Fröhlich coupling (∼23.4 nm) which is known as the predominant mechanism of linewidth broadening in hybrid MHPs. Thus, the linewidth broadening due to the quantum confinement (Δλ QC) is not a risk factor in the realization of MHP-based ultrahigh-quality next-generation LEDs.

Room-Temperature, Homogeneous, Single-Step, and Large-Scale Synthesis of Perovskite Nanoplatelets for Blue Light-Emitting Diodes

“…One approach used to synthesize blue-emitting IPNCs involves mixing chlorine and bromine as the X components in the ABX 3 perovskite structure. However, the blue emission peaks of IPNCs are often red-shifted or merge into single components of multipeak emission spectra due to phase separation induced by halide ion migration. − Hence, other researchers have explored reductions in at least one of the three dimensions for bromine-only IPNCs and the formation of nanostructures such as nanoplatelets (NPLs) to achieve induced quantum confinement. − In CsPbBr 3 , the exciton Bohr diameter is 7 nm, and quantum confinement occurs when the particle size is near or smaller than the exciton Bohr diameter. So, CsPbBr 3 NPLs consisting of a few monolayers (ML) exhibit blue emission. ,, Inorganic perovskite NPLs (IPNPLs) containing a single type of halide ion are not affected by halide ion migration, and their emission peaks are affected only by NPL thickness …”

Tuning optical properties of CsPbBr3 by mixing Nd3+ trivalent lanthanide halide cations for blue light emitting devices

“…The quantum confinement effect occurs when a particle's size is too small to be equivalent to an electron's wavelength. The tunable electronic levels are introduced by quantum confinement as the particle size decreases and eV increases respectively [45].…”