Electronic transport in films of colloidal CdSe nanocrystals

TL;DR

This study investigates electronic transport in large 3D arrays of CdSe nanocrystals, revealing power-law current decay, absence of steady-state current under high fields, and the significance of Coulomb interactions for long-lived transients.

Contribution

It provides the first detailed measurements of long-time electronic transport in colloidal CdSe nanocrystal films, highlighting power-law decay and Coulomb effects.

Findings

Power-law decay of current over five orders of magnitude in time

No steady-state dark current observed up to 10^6 V/cm

Long-range Coulomb interactions influence long-lived transients

Abstract

We present results for electronic transport measurements on large three-dimensional arrays of CdSe nanocrystals. In response to a step in the applied voltage, we observe a power-law decay of the current over five orders of magnitude in time. Furthermore, we observe no steady-state dark current for fields up to 10^6 V/cm and times as long as 2x10^4 seconds. Although the power-law form of the decay is quite general, there are quantitative variations with temperature, applied field, sample history, and the material parameters of the array. Despite evidence that the charge injected into the film during the measurement causes the decay of current, we find field-scaling of the current at all times. The observation of extremely long-lived current transients suggests the importance of long-range Coulomb interactions between charges on different nanocrystals.