Investigation of single layers of silicon quantum dots in SiO2 matrix for energy selective contacts in hot carriers solar cells

Structures consisting of silicon (Si) quantum dots (QDs) in an amorphous matrix have recently attracted research attention because of interesting optoelectronic properties. In this paper optical properties of devices consisting of a single layer of Si QDs in a silicon dioxide (SiO2) matrix are investigated. These structures show energy selection properties and are attractive candidates to realize Energy Selective Contacts (ESCs) for Hot Carrier Solar Cells (HCSCs). The HCSC is a promising third generation photovoltaic devices for which theoretical efficiencies of 66% for non concentrated AM1.5 solar radiation have been predicted by theoretical modelling. Transmission probabilities of Si QDs arrays in SiO 2 are modeled using Effective Mass Approximation (EMA) for a single electron and the results from simulations are compared with the experimental results. Several double barrier structures consisting of Si QDs in SiO2 have been realized using RFmagnetron co-sputtering, followed by high temperature annealing. The stoichiometry of the silicon rich oxide (SRO) layers has been investigated using near infrared-ultraviolet (UV-NIR) spectrophotometry and Rutherford backscattering (RBS). The formation of Si QDs has been confirmed using transmission electron microscopy (TEM) and Raman scattering measurements. Quantum confinement properties of single layer Si QDs between two SiO2 layers have been demonstrated.