Optoelectronic Properties of Ternary I–III–VI₂ Semiconductor Nanocrystals: Bright Prospects with Elusive Origins

Abstract

Colloidal nanocrystals of ternary I–III–VI 2 semiconductors are emerging as promising alternatives to Cd- and Pb-chalcogenide nanocrystals because of their inherently lower toxicity, while still offering widely tunable photoluminescence. These properties make them promising materials for a variety of applications. However, the realization of their full potential has been hindered by both their underdeveloped synthesis and the poor understanding of their optoelectronic properties, whose origins are still under intense debate. In this Perspective, we provide novel insights on the latter aspect by critically discussing the accumulated body of knowledge on I–III–VI 2 nanocrystals. From our analysis, we conclude that the luminescence in these nanomaterials most likely originates from the radiative recombination of a delocalized conduction band electron with a hole localized at the group-I cation, which results in broad bandwidths, large Stokes shifts, and long exciton lifetimes. Finally, we highlight the remaining open questions and propose experiments to address them.

Tailoring Cu+ for Ga3+ Cation Exchange in Cu2–xS and CuInS2 Nanocrystals by Controlling the Ga Precursor Chemistry

“…However, their large global Stokes shift and broad PL peak suggest that, similar to CIS and other I–III–VI 2 NCs, the PL in these nanomaterials most likely originates from the radiative recombination of a delocalized conduction band electron with a hole localized at a Cu(I) ion. 69 Time-resolved spectroscopic measurements could provide additional insights into the origin of the radiative recombination in these nanomaterials but are beyond the scope of the present work. It should be noted that the PL of these Pb- and Cd-free NCs is centered in the NIR biological window.…”

Tunable lanthanide/transition metal ion‐doped novel phosphors for possible application in w‐LEDs: a review

“…Spectroscopic studies are directly related to luminescence mechanisms and could be tuned by changing the size, composition, and surface of these nanomaterials. Luminescence centres showing broadband emission are susceptible to their coordination environment, therefore various emissions occurring due to the different activator sites in the same host crystal could drastically modify the nature of emission . Luminescence characteristics such as relative photoluminescence (PL) intensity of the band‐edge emission/defect‐site emission, and the peak wavelength of the band‐edge emission, were found to be dependent on the nature and concentrations of rare earth (RE) ions/transition metal ions due to change in the energy gap.…”

Simple Synthesis of CuInS2/ZnS Core/Shell Quantum Dots for White Light-Emitting Diodes

“…The II–VI (Cd-based) QDs have been thoroughly studied to be potentially toxic to the environment and humans (Chuang et al, 2014 ). For the other QDs, such as III–V (InP) (Zhang et al, 2019 , 2020 ), and ternary I–III–VI, such as Cu–In–S (CIS) (Gromova et al, 2017 ; Chen et al, 2018 ; Berends et al, 2019 ; Wegner et al, 2019 ), Cu–In–Se (Allen and Bawendi, 2008 ; Houck et al, 2019 ), quaternary Zn–Cu–In–S (Liu et al, 2015 ; Dai et al, 2017 ), and Ag–In–S (Ko et al, 2017 ) have been studied to replace the traditional Cd-based QDs. The CIS QDs have tunable emission wavelengths, greater stoke shifts, low toxicity, and low cost, which meets the requirements of down-conversion materials.…”