107 research outputs found
Selfconsistent Model of Photoconversion Efficiency for Multijunction Solar Cells
To accurately calculate efficiencies of experimentally produced
multijunction solar cells (MJSCs) and optimize their parameters, we offer
semi-analytical photoconversion formalism that incorporates radiative
recombination, Shockley-Read-Hall (SRH) recombination, surface recombination at
the front and back surfaces of the cells, recombination in the space charge
region (SCR) and the recombination at the heterojunction boundaries.
Selfconsistent balance between the MJSC temperature and efficiency was imposed
by jointly solving the equations for the photocurrent, photovoltage, and heat
balance. Finally, we incorporate into the formalism the effect of additional
photocurrent decrease with subcell number increase. It is shown that for an
experimentally observed Shockley-Read-Hall lifetimes, the effect of
re-absorption and re-emission of photons on MJSC efficiency can be neglected
for non-concentrated radiation conditions. A significant efficiency
increase can be achieved by improving the heat dissipation using radiators and
bringing the MJSC emissivity to unity, that is closer to black body radiation
rather than grey body radiation. Our calculated efficiencies compare well with
other numerical results available and are consistent with the experimentally
achieved efficiencies. The formalism can be used to optimize parameters of
MJSCs for maximum photoconversion efficiency.Comment: 40th IEEE Photovoltaic Specialists Conference, June 8-13, 2014,
Denver, Colorado, III-V Epitaxy and Solar Cells, F30 16
Hydrogen in non-crystalline materials: From solar cells to hydrogen Storage
The 3rd Annual Renewable Energy Symposium took place on the UNLV campus August 11 & 12. The event focused on renewable energy production in Nevada, the US Southwest, and renewable research projects nationwide. The event was a great success with over 200 individuals in attendance
First-principles calculation of the temperature dependence of the optical response of bulk GaAs
A novel approach has been developed to calculate the temperature dependence
of the optical response of a semiconductor. The dielectric function is averaged
over several thermally perturbed configurations that are extracted from
molecular dynamic simulations. The calculated temperature dependence of the
imaginary part of the dielectric function of GaAs is presented in the range
from 0 to 700 K. This approach that explicitly takes into account lattice
vibrations describes well the observed thermally-induced energy shifts and
broadening of the dielectric function.Comment: 6 pages, 3 figure
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