Seite - 174 - in Photovoltaic Materials and Electronic Devices

EnhancedErbium-DopedCeria NanostructureCoatingtoImproveSolar CellPerformance NaderShehata,MichaelClavel,KathleenMeehan,EffatSamir,SohaGaballah andMohammedSalah Abstract: This paper discusses the effect of adding reduced erbium-doped ceria nanoparticles (REDC NPs) as a coating on silicon solar cells. Reduced ceria nanoparticles doped with erbium have the advantages of both improving conductivity and optical conversion of solar cells. Oxygen vacancies in ceria nanoparticles reduce Ce4+ to Ce3+ which follow the rule of improving conductivity of solar cells through the hopping mechanism. The existence of Ce3+ helps in the down-conversion from 430 nm excitation to 530 nm emission. The erbium dopant forms energy levels inside the low-phonon ceria host to up-convert the 780 nm excitations into green and red emissions. When coating reduced erbium-doped ceria nanoparticles on the back side of a solar cell, a promising improvement in the solar cell efficiency has been observed from 15% to 16.5% due to the mutual impactof improvedelectricconductivityandmulti-opticalconversions. Finally, the impact of the added coater on the electric field distribution inside the solar cell has beenstudied. Reprinted fromMaterials. Cite as: Shehata, N.; Clavel, M.; Meehan, K.; Samir, E.; Gaballah, S.; Salah, M. Enhanced Erbium-Doped Ceria Nanostructure Coating to ImproveSolarCellPerformance.Materials2015,8, 7663–7672. 1. Introduction Optical nanostructures that emit visible light when excited by ultra-violet (UV) or infrared (IR) photons have been extensively studied for solar energy applications [1,2]. Recent research on one of these nanomaterials, cerium oxide (ceria) nanoparticles, has shown that its material properties are extremely well suited for a lot of applications [3–6]. Visible emission from either UV excitation (down-conversion) or IR excitation (up-conversion) can be obtained from ceria nanoparticles. However,bothup-anddown-conversionprocesses involvedifferent physiochemical properties in ceria and optimization of each optical process via various nanoparticle synthesis and post-growth procedures tends to quench the efficiencyof theotherprocess. 174