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Latest News from the Inorganic Chemistry

Dr. Julie Martins Gai




"Ln3+/Yb3+ codoped nanoparticles: New materials for near-infrared downconversion"

Siegen, October 2019


Current research topic:

Development and characterization of new down-conversion nanophosphors for efficiency enhancement of solar cells 

The worldwide growing demand for energy represents a major challenge, currently restrained by the available amount of non-renewable natural resources and therefore dangerous for the environmental preservation. Sun light, on the other hand, consist of an abundant energy source and represents, for this reason, a potential solution for this impasse. However, commercially available Si-based solar cells have a conversion efficiency of only approximately 15%. The reason for this low conversion rate is, mainly, mismatches between the solar spectrum irradiated on the earth surface and the light absorption spectrum of the photovoltaic cells. Hence, the most intensive radiation of the solar spectrum is emitted between 400 and 600 nm, while the Si solar cells absorb energy most intensively in the region of ca. 1000 nm. This phenomenon leads to the so-called thermalisation, or rather the heat loss generated by the absorption of a photon with energy larger than the energy gap of the solar cell (E > Eg), causing ca. 47% of the entire efficiency loss. 

The high-energy radiation of the solar spectrum could be more efficiently utilized by “cutting” it into two photons of lower energy, both more compatible with the absorption range of the solar cell panels. Quantum cutting, also known as down-conversion, can lead to quantum yields (QY) larger than 100% and is accomplished by doping appropriate host lattices with rare earth (RE) ions. Due to their unique and rich energy level structure, RE ions are promising candidates to allow the achievement of efficient down-conversion processes.


For practical applications, nanostructured phosphors are preferred to analogue micrometric or sub-micrometric materials, especially because their energy-saving synthesis techniques and high packing density. For instance, due to the reduced diameters, nanomaterials are able to build thinner phosphor films, requiring less material for coating the surface of the solar cells. Nevertheless, the high surface-to-volume ratio in nanoscopic host lattices is responsible for the creation of an extensively amount of lattice defects and the development of nanophosphors with high QY remains, for this reason, a substantial challenge.


During the doctoral research, different down-conversion materials will be developed, synthesized and characterized. Parameters, as the influence of the synthesis technique, host lattices, doping ions and their respective concentrations on the respective QY, will be investigated in order to increase the potential application of RE-doped nanomaterials in phosphor layers for solar cells, enhancing their efficiency.




C. C Silva, J. E. M Gai, L. A. A. Freitas, L. S. Freire, V. F. Veiga Junior; Inorganic Composition of Medicinal Plants. In: Vijay K. Gupta (editor), Natural Products: Research Reviews, 1st Ed., 2011, v. 1, p. 457-466.


Silva CC, Lima MCF, Gai JEM, Medeiros RS, Vieira G (2016) Energy Dispersive X-Ray Fluorescence Analysis of Amapá Milk (Brosimum ssp.). J Anal Bioanal Tech 7: 309. doi:10.4172/2155-9872.1000309




J. E. M. Gai, M. Campelo, C: C. Silva; “Composição inorgância do Leite de Amapá (Brosimum parinarioides, Brosimum potabile e Brosimum utile ovatifolium)”. National Week for Science and Technology, Superior School of Technology - State University of Amazonas, Manaus, Brazil, 2010.


J. E. M. Gai, M. Campelo, C: C. Silva, V. F. Veiga Junior; “Composição Inorgânica de Leite de Amapá (Brosimum parinarioides, Brosimum potabile e Brosimum utile ovatifolium).” In: 32nd Meeting of the Brazilian Chemical Society, Fortaleza, Brazil, 2009.


J. E. M. Gai, M. Hellmund, “Development of a Size Exclusion chromatography method to characterize N-Vinylpyrrolidone-polymers produced by millistructurated reactors” Bachelor Thesis, Universität Stuttgart, Stuttgart, 2013.


J. E. M. Gai, M. Campelo, C. C. Silva, “Composição inorgância do Leite de Amapá (Brosimum parinarioides, Brosimum potabile e Brosimum utile ovatifolium) utilizando EDX”. Internal Congress for Undergraduate Research, State university of Amazonas, Manaus, Brazil, 2010.

J. E. M. Gai, C. C. Silva, “Análise quali-quantitativa do etanol combustível comercializado na cidade de Manaus através de Fluorescência de Raios-X por energia dispersiva (EDX)”. Internal Congress for Undergraduate Research, State university of Amazonas, Manaus, Brazil, 2009.