Ga for Zn Cation Exchange Allows for Highly Luminescent and Photostable InZnP-Based Quantum Dots
Francesca Pietra (TU Delft - ChemE/Opto-electronic Materials)
Nick Kirkwood (TU Delft - ChemE/Opto-electronic Materials)
Luca De Trizio (Istituto Italiano di Tecnologia)
Nicolas Renaud (TU Delft - ChemE/Opto-electronic Materials)
Rolf Koole (Philips Lighting Research)
Patrick J. Baesjou (Philips Lighting Research, Universiteit Utrecht)
L. Manna (TU Delft - QN/van der Zant Lab, Istituto Italiano di Tecnologia, Kavli institute of nanoscience Delft)
AJ Houtepen (TU Delft - ChemE/Opto-electronic Materials)
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Abstract
In this work, we demonstrate that a preferential Ga-for-Zn cation exchange is responsible for the increase in photoluminescence that is observed when gallium oleate is added to InZnP alloy QDs. By exposing InZnP QDs with varying Zn/In ratios to gallium oleate and monitoring their optical properties, composition, and size, we conclude that Ga3+ preferentially replaces Zn2+, leading to the formation of InZnP/InGaP core/graded-shell QDs. This cation exchange reaction results in a large increase of the QD photoluminescence, but only for InZnP QDs with Zn/In ≥ 0.5. For InP QDs that do not contain zinc, Ga is most likely incorporated only on the quantum dot surface, and a PL enhancement is not observed. After further growth of a GaP shell and a lattice-matched ZnSeS outer shell, the cation-exchanged InZnP/InGaP QDs continue to exhibit superior PL QY (over 70%) and stability under long-term illumination (840 h, 5 weeks) compared to InZnP cores with the same shells. These results provide important mechanistic insights into recent improvements in InP-based QDs for luminescent applications.
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