Silver Ions as Ambipolar Dopants in InAs Nanocrystal Solids

The precise control of semiconductor polarity in nanocrystals (NCs) is crucial for optimizing device performance in various optoelectronic applications. In this study, it is shown that Ag⁺, added post-synthetically to InAs NCs using an AgNO₃ solution, can induce either n-type or p-type doping of the solid, depending on the intrinsic polarity of the host and the dopant concentration. In n-type InAs NCs, Ag⁺ consistently acts as an interstitial n-type dopant, shifting the conduction band minimum closer to the Fermi level. Conversely, in p-type InAs NCs (innately doped with Zn during synthesis), Ag⁺ initially exhibits a p-type doping effect at low concentrations by forming surface dipoles but transitions to an n-type doping effect at higher concentrations through interstitial incorporation. These results offer a unified understanding of the intricate and adjustable doping behavior of Ag⁺ in colloidal NC systems and present new opportunities for post-synthetic polarity engineering in III-V nanomaterials.