PhD candidate: Elisabeth PAYRER
Date and place of defence: February 12, 2014 - Université de Grenoble, France.
The development of high efficiency solar cells is a key challenge for the next years. Solar cells are photovoltaic devices which convert radiant solar energy into electrical energy. They are based on the photogenerated current created in semiconductor devices which only absorb light whose wavelength is shorter than a cut-off value, corresponding to photon energies above the bandgap of the absorbing layer. The cut-off wavelength is usually located in the near-infrared (~ 800 nm), especially for materials suitable for low-cost thin-film solar cell technology (a-Si:H, CdTe, etc.), so a significant part of the solar energy is lost. The techniques currently available to utilize the large unused infrared light fraction of the solar spectrum, e.g. multi-junction and tandem cells, all are very expensive.
A new approach, based on the up-conversion technique, may provide a cheap and simple way to convert some of the infrared into visible light and send it back to the solar cells, therefore improving their energy harvesting efficiency.
The up-conversion phenomena will be studied and optimized in Rare-Earth doped oxide and fluoride thin films deposited by Sol-Gel or MOCVD methods, utilizing different physico-chemical characterization techniques (XRD, FEG-SEM, TEM, EDX-WDX, plus FTIR and Raman spectroscopies), as well as photoluminescence measurements.
IST - ICEMS Lisbon
INPG - LMGP Grenoble