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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Design of Efficient Solar Energy Materials from Theory(DESEMAT)

Awarded: NOK 5.4 mill.

The main objective of the DESEMAT project is to use computational modelling to understand how chemistry, structure and defects influence the properties of transparent thin oxide layers that may enhance performance of next generation solar cell components. Although the basic oxides, their atomic arrangement and their growth/synthesis is well known, it remains quite open how one should go ahead in order to tailor and engineer materials to optimize electronic conductivity while keeping excellent optical transparency. Modeling has in this respect important benefits; in the computer one may define compositions, defects and agglomerates of defects in well-defined manners, and perform calculations on how they ideally will affect key physical properties. The synthesis and detailed characterization is on the other hand far more challenging. Hence, our idea is to combine such approaches, however, in DESEMAT the emphasis has been on modelling, to some extent complemented by experiments. Focus has been put on two categories of important classes of compounds; first of all, on ZnO and variants holding defects and defects complexes; second on p-type ABO2 delafossite type oxides (where electron holes mediate the electronic transport). The obtained results have been presented at some 10 talks and posters, and in 6 publications. We have been able to explain various photoluminescence spectra in ZnO based on modelled defect clusters; we have described issues and potential pathways for using Li-doping to achieve p-type ZnO; we have identified likely origin for the so-called hidden hydrogen in ZnO, and we have concluded that CuNdO2 is the best p-type conductive oxide among the delafossites oxides (ABO2, A = Ag and Cu; B = Al, Ga, In, Sc, and Y). The project has been interfaced with activities in the FME on solar cell technology, and with synthesis and characterization activities on functional oxides in the NAFUMA research group. In this way DESEMAT has contributed in an important and efficient way to competence building.

The solar energy resource is enormous and corresponds to almost 6,000 fold the current global consumption of primary energy (13.7TW). Thus, solar energy has the potential of becoming a major component of a sustainable energy portfolio aimed at reducing th e global emissions of greenhouse gasses into the atmosphere. Nevertheless, the current use of this energy resource represents less than 1% of the total electricity production from renewable sources. From a scientific and technical viewpoint, the developme nt of new technologies with higher conversion efficiencies and low production costs is a key requirement for enabling the deployment of solar energy at a large scale. So, the main objective of the present project is to understand the fundamental physical properties of optoelectronic materials useful for new generation solar cells using state-of-the-art density functional calculations and gained knowledge will be transferred to experimentalists at UoO to optimize potential materials for highly efficient so lar cell. We aim at studying role of surfaces, interfaces, and defects on optoelectronic properties of bulk and thin film nanostructures to elucidate the structure-property relationships of these materials. This will help to build competence in nanoscale design of efficient energy generation materials. In order to obtain more efficient and cheap solar-energy materials, we propose a four-pronged approach suchs as (i) Make transparent conducting oxides film over existing Si solar cells; (ii) Band-gap engine ering, and (iii) Forming variable band gap multi-junction solar cells, and (iv) Optical properties of TCOs.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek