Voznyy O, Thon S M, Ip A H, Sargent E H
Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada.
J Phys Chem Lett. 2013 Mar 21;4(6):987-92. doi: 10.1021/jz400125r. Epub 2013 Mar 11.
Using first-principles simulations on PbS and CdSe colloidal quantum dots, we find that surface defects form in response to electronic doping and charging of the nanoparticles. We show that electronic trap states in nanocrystals are dynamic entities, in contrast with the conventional picture wherein traps are viewed as stable electronic states that can be filled or emptied, but not created or destroyed. These traps arise from the formation or breaking of atomic dimers at the nanoparticle surface. The dimers' energy levels can reside within the bandgap, in which case a trap is formed. Fortunately, we are also able to identify a number of shallow-electron-affinity cations that stabilize the surface, working to counter dynamic trap formation and allowing for trap-free doping.
通过对硫化铅和硒化镉胶体量子点进行第一性原理模拟，我们发现表面缺陷是在纳米颗粒发生电子掺杂和充电时形成的。我们表明，纳米晶体中的电子陷阱态是动态实体，这与传统观点不同，传统观点认为陷阱是可以被填充或清空，但不能被创造或破坏的稳定电子态。这些陷阱源于纳米颗粒表面原子二聚体的形成或断裂。二聚体的能级可以位于带隙内，在这种情况下就会形成一个陷阱。幸运的是，我们还能够识别出一些能稳定表面的浅电子亲和性阳离子，它们有助于对抗动态陷阱的形成，并实现无陷阱掺杂。
