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Download fileConfinement Effects and Charge Dynamics in Zn3N2 Colloidal Quantum Dots: Implications for QD-LED Displays
journal contribution
posted on 2019-11-05, 00:03 authored by Ruben Ahumada-Lazo, Simon M. Fairclough, Samantha J. O. Hardman, Peter N. Taylor, Mark Green, Sarah J. Haigh, Rinku Saran, Richard J. Curry, David J. BinksZinc nitride (Zn3N2) colloidal quantum dots
are composed of nontoxic, low-cost, and earth-abundant elements. The
effects of quantum confinement on the optical properties and charge
dynamics of these dots are studied using steady-state optical characterization
and ultrafast fluence-dependent transient absorption. The absorption
and emission energies are observed to be size-tunable, with the optical
band gap increasing from 1.5 to 3.2 eV as the dot diameter decreased
from 8.9 to 2.7 nm. Size-dependent absorption cross sections (σ
= 1.22 ± 0.02 × 10–15 to 2.04 ± 0.03
× 10–15 cm2), single exciton lifetimes
(0.36 ± 0.02 to 0.65 ± 0.03 ns), as well as Auger recombination
lifetimes of biexcitons (3.2 ± 0.4 to 5.0 ± 0.1 ps) and
trions (20.8 ± 1.8 to 46.3 ± 1.3 ps) are also measured.
The degeneracy of the conduction band minimum (g =
2) is determined from the analysis of the transient absorption spectra
at different excitation fluences. The performance of Zn3N2 colloidal quantum dots thus broadly matches that of
established visible light emitting quantum dots based on toxic or
rare elements, making them a viable alternative for QD-LED displays.