Tandem PV cells - with their increased efficiency due to a multi-band gap approach - usually involve expensive materials and fabrication. Thin film approaches, with an engineered variation in band gap through the use of quantum confinement in Si quantum dots, offer a cheaper alternative. Presented are characterisation and modelling data on fabrication of such Si and Sri QD nanostructures in various dielectric matrices by self-organised thin film deposition, with demonstrated confined energy levels of 1.7 eV for 2 nm diameter QDs. This being the optimum energy for an upper tandem cell element. (c) 2008 Elsevier B.V All rights reserved.