Progress toward Producing n-Type CdSe Quantum Dots: Tin and Indium Doped CdSe Quantum Dots

Abstract

Controlling conductivity via doping in semiconductor quantum dots is an important part of nanoparticle research. In this report, doping of CdSe quantum dots with indium and tin is explored. High-resolution nanoprobing confirms the presence of indium and tin in the particles and the inclusion of indium into the particles without forming a separate phase. The tin doped CdSe samples show preferential adsorption of tin in quantum dots from the solution during synthesis while incorporation of indium is somewhat statistical. In agreement with the expected n-type behavior, the photoluminescence (PL) of both indium and tin doped samples exhibits a significantly steeper temperature dependence, compared to undoped CdSe quantum dots. Comparison of theory and experimental data suggests that the approximate locations of the dopants levels are at 280 and 100 meV below the conduction band edge of the indium and tin doped quantum dots, respectively. The relative temperature dependent Stokes shifts of the doped samples are larger than those of the undoped sample, suggesting that the electron is backfilling the lowest unoccupied quantum dots levels. The oxidized doped samples exhibit increased polarized band-edge emission. The likely explanation of the polarized emission is that trapping times are fast in the oxidized doped samples compared to the undoped samples.

Designing Metallic and Insulating Nanocrystal Heterostructures to Fabricate Highly Sensitive and Solution Processed Strain Gauges for Wearable Sensors

“…After EDT ligand exchange, pure Au NC thin films showed significantly reduced resistivity of 90.1 Ω cm. However, pure CdSe NC thin films showed electrically insulating properites as CdSe NCs have very low electron density due to their intrinsically wide band gap unless they are heavily doped . 27%, 45%, 59%, and 77% CdSe NC hybrid thin films showed intermediate electrical properties with resistivity of 1.7 × 10 2 , 4.4 × 10 2 , 4.1 × 10 3 , and 4.6 × 10 5 Ω cm, respectively ( Table 1 ).…”

Strategies for the Controlled Electronic Doping of Colloidal Quantum Dot Solids

“…Several works exist on doping CdSe CQDs with Ga, [68] Al, [108] or In, [108][109][110][111][112] whichw hen ionizeda tt heir preferred + 3o xidation state and substituting Cd 2 + should act as donors of electrons at (closer to) the conduction band. Wills et al doped CdSe in solution with Al and In.…”

Electronic Impurity Doping in CdSe Nanocrystals

“…12, 16,24 Here, we analyze CdSe nanocrystals that are lightly doped with Ag. Herein, we use the phrase "lightly doped" to indicate that only a few impurities are added to each nanocrystal.…”