Effects of size polydispersity on electron mobility in a two-dimensional quantum-dot superlattice

We found that the transitions between delocalized electronic states in quantum-dot superlattices with smaller size dispersion can account for higher electron mobility. In particular, we solved for the quantum states of a two-dimensional quantum-dot (QD) superlattice using a one-electron approximation. Electron transport properties were studied by considering hopping transitions among coupled delocalized electronic states. Molecular dynamics simulations were employed to introduce disorders in superlattice configurations as a function of QD size and size dispersion for calculation of electron mobility. The interparticle spacing, size, and temperature dependence of the electron mobility can be well explained within the framework of our analysis.

Figure 1

Coupling energy (a), reorganization energy (b), and electron mobility (c) as functions of ligand length. The QD average diameter is 6.0 nm with 3% or 5% standard deviation. This is compared with the case with experimental data from Liu et al. [17].

Figure 2

(a) Electron mobility as a function of QD diameter. (b) Scatter plot showing the spread of activation energy and coupling energy for QD assemblies with different average sizes. The ligand length is 0.45 nm, and the size deviation is 3%.

Figure 3

Log-log plot of $d(log(\mu \left)\right)/d(logT)$ vs T (a), reorganization energy vs QD average size (b), and Arrhenius plots (c) of electron mobility for QD assemblies with different average sizes.

Figure 4

Total electron probability density weighted by the Fermi-Dirac distribution with different size dispersion. Red indicates high probability density, and blue is for lower values.

Figure 5

Delocalization of electron wave functions (a), coupling energy (b), reorganization energy (c), and room-temperature mobility versus surface energy density (d) with various size dispersion cases.