  A high photon to electricity conversion efficiency of 47.2082% was achieved
by a novel combination of In0.51Ga0.49P, GaAs, In0.24Ga0.76As and
In0.19Ga0.81Sb subcell layers in a quadruple junction solar cell design. The
electronic bandgap of these materials are 1.9 eV, 1.42 eV, 1.08 eV and 0.55 eV
respectively. This novel III-V arrangement enables the cell to absorb photons
from the ultraviolet to deep infrared wavelengths of the solar spectrum. After
careful consideration of important semiconductor parameters such as thicknesses
of emitter and base layers, doping concentrations, diffusion lengths, minority
carrier lifetimes and surface recombination velocities an optimized quadruple
junction design has been suggested. Current matching of the subcell layers was
ensured to obtain maximum efficiency from the proposed design. The
short-circuit current density, open circuit voltage and fill factor of the
solar cell are 14.7 mA/cm2, 3.3731 V and 0.9553 respectively. In the design
process, 1 sun AM1.5 global solar spectrum was considered. The cell performance
was also investigated for extraterrestrial illumination (AM0). A modified
design is proposed for space applications. With a short circuit current density
of 18.5 mA/cm2, open circuit voltage of 3.4104 and the fill factor of 0.9557,
the power conversion efficiency of the modified quadruple junction design is
44.5473% in space.
