Highly ordered quantum dot (QD) arrays are of interest for use as absorber materials in Hot Carrier solar cells. In such a cell carrier thermalization must be slowed and restriction of specific phonon modes – which can occur in these ordered QD arrays – has been shown to potentially exhibit such slowing of carrier cooling [1]. This project strives to create an ordered monolayer from colloidal dispersions of Si NPs. By means of Langmuir-Blodgett (LB) technique to construct the monolayer and wet chemistry methods to encapsulate the Si NPs with organosilanes, we seek to fabricate a highly ordered Si molecular film.

The LB technique leads to the development of ordered monolayers at an air-water interface using sophisticated apparatus while exploiting the self-organization mechanism of the colloidal dispersion. This unique technique allows transfer of a monolayer onto a wide range of solid substrates such as glass or Si wafers. The spacing between adjacent NPs can be manipulated by varying the alkyl chain lengths of organosilanes that can be bound to the Si NPs, essentially “capping” or surface passivating the particles.

Work is underway to characterise Si QDs suspended in toluene. Characterisation includes UV-visible spectroscopy to investigate the absorption of the NPs, scanning and transmission electron microscopy to analyse size distribution, alongside photoluminescence to study emission spectra of the NPs. Structural and optical properties will be discussed. Future work includes the formation and characterisation of the constructed Si NP monolayer.

[1] Conibeer et al., Proc. 21st European PVSEC (Dresden, 2006), 47.