TRAnsition metal and LAnthanide based Luminescent Absorber Layers by Ald

Solar cells have become an important part of the future and show exponential growth in use. The cells are cheap, robust and require little maintenance. The costs of installing solar cells today mainly go to packaging and assembly. A gain in efficiency of the cell itself will therefore quickly be multiplied when it is transferred to the rest of the links in the value chain. The Tralalala project aims to investigate alternative ways to increase the efficiency of solar cells. Tralalala has focused on changing the wavelength of the light that falls on a solar cell to better match what silicon solar cells can best utilize. The project is based on CaMoO4 as absorber material as the Mo-O bond has a very efficient charge-transfer absorption in a suitable optical range. When the photon is absorbed, it is transferred on to Pr and then Yb, which gives luminescence at a wavelength that fits very well with the band gap of Si. By using CaMoO4 as the absorber material, we only need trace amounts of Pr and Yb to achieve effective luminescence. This method is possible with the deposition technique used (ALD = atomic layer deposition) as it allows good control of the distance between the dopants used. This is necessary to limit unwanted loss of efficiency. On the way to the goal, the project has also developed a new process for depositing MoO3 which also shows inherent selective growth. With this process, it is possible to combine growth and lithography in one and the same process, and in that way only deposit MoO3 where it is wanted. Such processes are very rare and the discovery was found as a serendipity.

Utdannet en PhD kandidat og trent en ung forsker i prosjektledelse. Økt internasjonalt samarbeid gjennom utveksling og samarbeid med Universitetet i Utrecht. Utviklet en ny prosess for MoO3 som viser iboende selektiv vekst med ALD. Dette er uvanlig og åpner for nye måter å se etter slike egenskaper. Første vei for fremstilling av CaMoO4 med ALD, samt vist hvordan verktøyet Design of Experiments kan benyttes til effektiv forsøksplanlegging. Prosjektet har vist hvordan ALD kan brukes til å undersøke optiske utvekslingsmekanismer ved å kontrollere avstanden mellom optisk aktive komponenter i materialer. Slik design av optiske koblingsmekanismer er relativt ukjent ved bruk av tynne filmer. Således er prosjektet en god mal for videre undersøkelse av slike fenomener for effektiv luminescens og kontroll av defekter som ellers leder til tap av effektivitet.

The project aim to develop unprecedented Down-Conversion coatings of top relevance for technology in next generation Silicon based solar cells by combining skills in materials growth, local structure characterization, measurements of optical properties and DFT modeling. The underlying idea is to utilize an intelligent distribution of luminescent rare earth cations in an adequate matrix that will enable down shifting of photon energies into the absorption range of silicon. The distribution of rare earth elements and structural tuning of the matrix will be achieved through growth of multilayered structures of complex materials as well as homogeneously distributed doped materials by the Atomic Layer Deposition (ALD) technique in manners already demonstrated by the applicants. A key characterization concerns measurements that provide information of the local structure of the dopants and their possible defect complexes. Here, synchrotron based methods will be utilized at ESRF, Grenoble. The characterization of local and average structure, electronic and optical properties, will be complemented by state-of-the-art DFT modeling, partly along with international partners. The project will interact with Norwegian R&D related to solar cell technology via the FME on solar cell technology. The requested resources, one PhD and one post doctor/researcher, will work in close interaction with specialists in the NAFUMA and LENS research groups at the Centre for materials science and nanotechnology, UiO, as well at the solar center, IFE, Kjeller, thereby benefiting from recognized competences at a high international level. The Project will heavily use national infrastructure (RECX, NORTEM, NICE, NORFAB, NOTUR).