Photovoltaics is becoming an increasingly important field, focusing on obtaining electricity from renewable energy sources – the sun. It is important to further decrease solar cells manufacturing costs and to achieve higher conversion efficiencies. Better efficiency is also desired. Thin-film solar cells present a solution that could tackle previously mentioned requirements.
The thesis deals with the improvement of light trapping in solar cells, increasing their efficiency. In particular, we investigated the role of metal nanoparticles introduced in the cell to scatter light. With the help of tree-dimensional optical simulations we have tackled effects and shown improvements in light trapping, for the case of thin-film silicon solar cell, based on microcrystalline material. Due to plasmonic effect, metal nanoparticles effectively dissipate light at high angles, which is vital for light trapping in a solar cell. In our simulations, we placed silver nanoparticles at different positions within the front and back transparent conductive layer. We focused our simulations on spherical metal nanoparticles. For the best position, we also tested various dimensions of metal nanoparticles and several distances between nanoparticles. All 3D models were designed and simulated by Comsol software. For each individual case we calculated solar cell’s quantum efficiency QE, short-circuit current density JSC and total light reflection Rtot measured on top of the solar cell. We concluded that metal nanoparticles in the back TCO cause an increase in short-circuit current density even for cells with textured interfaces. Best results were obtained when nanoparticles were positioned close to the doped n layer. Here, we noticed that increasing the diameter of metal nanoparticles causes an increase of short-circuit current density, but only to a certain point. Moreover, we noticed that for longer wavelengths, all simulations brought an increase in solar cell’s quantum efficiency QE. Lastly, we reviewed the influence of different spacing between metal nanoparticles, on QE, JSC and Rtot. Both, short-circuit current density and quantum efficiency (especially for long wavelengths), show an increase in value when nanoparticles are moved closer together.
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