Silicon nanocrystals embedded in a dielectric matrix behave as quantum dots (QD) when they have very small dimensions (< 10 nm in diameter): they can be used to engineer structures whose band gaps are finely tunable by adjusting the nanocrystals size. Such structures have been proposed to be employed in “all-Si” tandem cells, composed by several solar cells of different band gaps stacked on top of one another, with the highest band gap cell uppermost: each cell absorbs a slice of the solar spectrum, with below band gap photons passing through to underlying cells.
Aim of the work is to set up the methodologies for fabricating (by sputtering or PECVD) amorphous thin film structures formed by Si-nanocrystals embedded in silicon nitride dielectric matrices by laser or thermal annealing. We will also exploit the possibility of preparing and testing hybrid organic-inorganic cells by employing cheap deposition technologies: inkjet printing of the polymeric matrix precursor blended with the inorganic nanocrystalline fillers and UV curing of the cell on flexible substrates.
The research will concern the study of the quantum confinement effects, of the electronic transport properties and of the correlation between the properties and the nanocrystals dimensions. Dopants incorporation in nanocrystals, which is essential to increase carrier populations and to fabricate a p-n junction, will be obtained by using a dedicated co-sputtering system.