Photoconductivity in aligned CdSe nanorod arrays

The voltage dependence of the phototransport in colloidal CdSe nanorods (NRs) arrays was studied for different capping molecules and degree of NR alignment. The photocurrent was found to considerably enhance by exchanging the trioctylphosphine capping ligands by diamine molecules or upon annealing. The corresponding current-voltage characteristics were highly nonlinear, showing, in the aligned NR arrays, a notable decrease in the differential conductivity at a certain capping-molecule-dependent applied electrical field. This transition smears, however, when the degree of NR alignment is reduced. These findings are well described by an exciton field-ionization model, which also accounts for the correlation we observe between the photocurrent I (V) curves and the voltage dependence of the fluorescence quenching in seeded-grown CdSe/CdS core/shell NR films.