Pietra Francesca, Kirkwood Nicholas, De Trizio Luca, Hoekstra Anne W, Kleibergen Lennart, Renaud Nicolas, Koole Rolf, Baesjou Patrick, Manna Liberato, Houtepen Arjan J
Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
Department of Nanochemistry, Istituto Italiano di Tecnologia (IIT), via Morego, 30, 16163 Genova, Italy.
Chem Mater. 2017 Jun 27;29(12):5192-5199. doi: 10.1021/acs.chemmater.7b00848. Epub 2017 Jun 6.
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 Ga preferentially replaces Zn, 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.
在本工作中，我们证明了在油酸镓添加到InZnP合金量子点时观察到的光致发光增强是由优先的Ga-Zn阳离子交换引起的。通过将具有不同Zn/In比的InZnP量子点暴露于油酸镓并监测它们的光学性质、组成和尺寸，我们得出结论，Ga优先取代Zn，导致形成InZnP/InGaP核/梯度壳量子点。这种阳离子交换反应导致量子点光致发光大幅增加，但仅对于Zn/In≥0.5的InZnP量子点。对于不含锌的InP量子点，Ga很可能仅掺入量子点表面，未观察到光致发光增强。在进一步生长GaP壳层和晶格匹配的ZnSeS外壳层后，与具有相同壳层的InZnP核相比，阳离子交换后的InZnP/InGaP量子点在长期光照（840小时，5周）下仍继续表现出优异的光致发光量子产率（超过70%）和稳定性。这些结果为基于InP的发光应用量子点的近期改进提供了重要的机理见解。
