  A high theoretical efficiency of 47.2% was achieved by a novel combination of
In0.51Ga0.49P, GaAs, In0.24Ga0.76As and In0.19Ga0.81Sb subcell layers in a
simulated quadruple junction solar cell under 1 sun concentration. The
electronic bandgap of these materials are 1.9 eV, 1.42 eV, 1.08 eV and 0.55 eV
respectively. This unique arrangement enables the cell absorb photons from
ultraviolet to deep infrared wavelengths of the sunlight. Emitter and base
thicknesses of the subcells and doping levels of the materials were optimized
to maintain the same current in all the four junctions and to obtain the
highest conversion efficiency. The short-circuit current density, open circuit
voltage and fill factor of the solar cell are 14.7 mA/cm2, 3.38 V and 0.96
respectively. In our design, we considered 1 sun, AM 1.5 global solar spectrum.
