Solution-Processed Networks of Silicon Nanocrystals: The Role of Internanocrystal Medium on Semiconducting Behavior

We have produced networks of surface-oxidized and hydrogen-terminated silicon nanocrystals (Si-NCs), both intrinsic and n-type doped, on flexible plastic foil from nanoparticle inks. The charge transport in these networks was comprehensively studied by means of time-dependent conductivity, steady-state current versus voltage characteristics, and steady-state photocurrent measurements as a function of incident light intensity. These measurements were complemented by surface chemistry and structural/morphological analysis from Fourier transform infrared spectroscopy and electron microscopy. Whereas H-terminated Si-NC networks function as semiconductors (both in air and in vacuum), where conductivity enhancement upon impurity doping and photoconductivity were observed, these characteristics are not present in networks of surface-oxidized Si-NCs. For both network types, the observation of a power law behavior for steady-state current versus voltage and a current decaying with time at constant bias indicate th...