n-Type PbSe Quantum Dots via Post-Synthetic Indium Doping

Abstract

We developed a post-synthetic treatment to produce impurity n-type doped PbSe QDs with In 3+ as the substitutional dopant. Increasing the incorporated In content is accompanied by a gradual bleaching of the interband first-exciton transition and concurrently the appearance of a size-dependent, intraband absorption, suggesting the controlled introduction of delocalized electrons into the QD bandedge states under equilibrium conditions. We compare the optical properties of our In-doped PbSe QDs to cobaltocene treated QDs, where the n-type dopant arises from remote reduction of the PbSe QDs and observe similar behavior. Spectroelectrochemical measurements also demonstrate characteristic n-type signatures, including both an induced absorption within the electrochemical bandgap and a shift of the Fermi-level towards the conduction band. Finally, we demonstrate that the In 3+ dopants can be reversibly removed from the PbSe QDs, whereupon the first exciton bleach is recovered. Our results demonstrate that PbSe QDs can be controllably n-type doped via impurity aliovalent substitutional doping.

Mercury Chalcogenide Quantum Dots: Material Perspective for Device Integration

“…Note that this process is no longer limited to mercury chalcogenides and has been recently observed for PbS(e) NCs. [225][226][227] Because the confinement drives absorption spectrum, the largest particles have the reddest absorption. The doping magnitude is also controlled by the confinement through the relative position of the conduction band with respect to the Fermi level, the highest doping is thus achieved for the largest particles.…”

Spectroelectrochemistry of Quantum Dots

“…UV/VIS‐SEC was used to demonstrate characteristic n‐type signatures of In 3+ doped PbSe QDs, Figure , including both an induced absorption within the electrochemical bandgap and a shift of the Fermi level toward the conduction band …”

“…[93] UV/VIS-SEC was used to demonstrate characteristic ntype signatures of In 3 + doped PbSe QDs, Figure 11, including both an induced absorption within the electrochemical bandgap and a shift of the Fermi level toward the conduction band. [115] PL-SEC experiments on Cu-doped core/shell ZnSe/CdSe NCs were used to probe the PL intensity and branching ratio between the band edge and the Cu related emission channels as a function of controlled activation and deactivation (passivation) of surface traps. By raising/lowering the Fermi level, the occupancy of surface trap sites can be modified.…”

“…Overall, increasing In content in PbSe QDs leads to more n-type character (smaller ΔE f ). Adapted with permission from Ref [115]. Copyright 2018 American Chemical Society.…”

InAs Nanocrystals with Robust p‐Type Doping

“…To this end, we reported on impurity doping of InAs nanocrystals, which brings them to the regime of heavy doping as reflected in the optical properties, scanning tunneling spectroscopy data for single isolated nanocrystals and theoretical analysis. [21] Impurity doping was also reported for CdSe [38][39][40] and Pb chalcogenide [30,32,37,[41][42][43] NCs, which serve as outstanding model systems but are limited in terms of applicability by health and environmental hazard regulations. This provides further motivation to pursuit doping of III-V SC NCs as promising building blocks for optoelectronic NC devices [29,44] due to their relatively low toxicity, high carrier mobility and their optical properties, which are tunable across the visible to the near IR.…”