Structure and dynamics in photovoltaic metal hydrides

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Australian Institute of Physics
Solar cell technology is an active area of research with the quest to improve the efficiency of solar cells to above the current value of 44%. Hot carrier solar cells are particular types of cells which may enable higher efficiencies to be obtained. However, these are only feasible where there is a sufficiently large band gap in the phonon dispersion of the bulk material to minimise energy loss to thermalisation, thus keeping the electrons ‘hot’. Binary compounds with a large mass difference between the two constituent atoms, and high level of crystal symmetry such as titanium hydride, can have such a gap in their phonon dispersion. Titanium hydride is an interesting photovoltaic material with a broad range of properties, which vary depending on the proportion of hydride present. Theoretical studies show TiH2 has a phonon band gap of 95 meV in the bulk phase, however, experimentally this compound exists as a powder because the hydrogenation process causes large stresses in the lattice which are strong enough to crack the bulk sample. For solar cell absorber materials, a bulk sample is preferred and these can be manufactured by hydrogenating very pure Ti metal. We have previously studied TiH1.65 using X-ray powder diffraction and inelastic neutron scattering and found that while the width of the acoustic and optical phonon bands is different from those of TiH2, it did have a phonon band gap of 65 meV i.e. large enough to block Klemens’ decay. We present here an extension of this work with Fourier Transform Infra-red (FTIR) and Raman spectroscopy, along with X-Ray Diffraction (XRD) data from the photovoltaic materials, TiH2 and ZrH2.
Coherent scattering, Diffraction, Dimensionless numbers, Direct energy converters, Elementary particles, Elements, Equipment, Fermions, Hydrogen compounds, Integral transformations, Laser spectroscopy, Leptons, Mechanics, Metals, Photoelectric cells, Photoelectric effect, Photovoltaic cells, Quasi particles, Scattering, Solar equipment, Spectroscopy, Transformations, Transition elements
Chea, K., Greaves, T., Le, T., Rule, K., Mole, R. A., Wang, P., Shrestha, S., Conibeer, G., & Iles, G. N. (2018). Structure and dynamics in photovoltaic metal hydrides. Poster presented to the 42nd Annual Condensed Matter and Materials Meeting Charles Sturt University, Wagga Wagga, NSW 30th January – 2nd February, 2018. (pp. 89). Retrieved from: