Towards silicon nanocrystals based solar cells: Morphological properties and conduction phenomena

In this work, we present the fabrication and the structural and electrical characterization of quantum confined silicon nanodots for advanced 3rd generation photovoltaic cells. Silicon permits its bandgap control by forming quantum confined nanocrystals in SiO2 (diameter < 10 nm) and allowing a bandgap of more than that of the bulk (1.1 eV). We examine the properties of such films of SiO2 with embedded silicon nanocrystals (nc-Si) of diameter ≈ 5 nm. Techniques like GIXRD, HRTEM, FTIR, XPS and spectroscopic ellipsometry have been used to investigate the film structure, size and distribution of the nanocrystals. Contrary to expectations from a largely dielectric material, significant conduction has been observed in our nc-Si embedded SiO2 film. This conduction, likely to be via the nanodots, is a promising result for integration into photovoltaic devices.