Final Report Summary - ULTRA PARTICLE (Ultra precise nanoparticles to harvest light) Solar energy is an attractive source of alternative energy contributing to fossil fuel independence.Research is still needed to bring down the cost of solar cells for commercial use. For this, novel concept solar cell research make use of low cost materials with novel techniques, often at the nanoscale. The main aim of this grant proposal lays in the development of ultra precise nanoparticles with sizes where quantum confinement becomes dominant. A nanoparticle source (gas aggregation in vacuum) has enabled the production of ultra precise nanoparticles (silicon, germanium, etc), i.e. high size control. A second research theme was the use of plasmonics of metal nanostructures (particles) to enhance optical absorption in solar cells.Work performedUpon acceptance of this project by the EU commission, a state-of-the-art cluster source has been purchased from Oxford Applied Research together with the necessary consumables and supplies.After approximately 4 months the cluster source was delivered and over the next period of about 2 months was assembled and connected to an already available thin film sputter device. From about January 2012 the first samples were produced. Both silver, silicon and germanium nanoparticles were deposited on various substrates. The Ag, Al, Si, TiO2 particles were characterised by various methods like atomic force microscopy and transmission electron microscopy. Since the particle morphology looked promising the next step of embedding Ag particles in amorphous silicon was undertaken. This is a first step towards using the plasmonic properties of metal particles in Si based materials for enhanced photo absorption in solar cells. A detailed study of silver particles in a-Si was performed in the period September 2012 until February 2013. Simulations completed the data. In March 2013 the production of silicon nanoparticles of a size within the quantum confinement limit, which make them interesting for photovoltaics, had a sufficient yield to be able to make thin nanoparticle assembled films. The results of the Si particles are published. Aluminium particles inside a-Si and SiN are studied with conclusive results. TiO2 Mie scatterers are investigated with the same methods, resulting in enhanced absorption. EELS measurements were performed on silver nanoparticles embedded in Sin (collaboration with DTU) by which the plasmonic response was measured, yielding a quadrupole resonance.Main results: 1) Setting up a novel cluster source combined with thin film deposition. 2) Control over various production parameters of metal and semiconducting nanoparticles for PV 3) study of plasmonics of Ag nanoparticles in a-Si. 4) Si QD layers for PV.5) aluminium particles for enhanced photo absorption, 6) TiO2 Mie scatterers for enhanced photo absorption 6) EELS measurements on silver particles embedded in SiN provided a quadrupole resonance with quantum effects making it disappear.The outcomes of this project are focussed on increasing solar cell performance with novel structures at the nanoscale. The first steps to use Si QD systems from gas aggregation cluster sources are demonstrated. The study of Ag and aluminium plasmonic particles demonstrated significant effects and will be published. The TiO2 Mie scatterers also provided strong absorption effects in thin films, which may prove to be useful for photovoltaics. EELS results on Ag particles embedded in SiN show interesting plasmonic behaviour. A substantial increase of PV efficiency has a direct impact on how our society harvests energy. It will enable cheaper electricity production and provide energy supply independence. But perhaps more important, it has a considerable positive effect on the environment as no fossil fuels or other potentially damaging products are used.Output of the project was negatively influenced by a reorganization within the Faculty of Science. At the first year of this Marie Curie project this reorganisation canceled the researchers group. Although he was allowed to continue his work (under a full regular employment contract) until the end of this MArie Curie project, he was not suitably embedded anymore and was not allowed to submit proposals.
