  In this paper we study CdS/CdTe solar cells by means of AMPS-1D software.
First we study the effect of thickness of semiconductor layers on the output
parameters of the CdS/CdTe solar cell, such as density of short-circuit
current, open circuit voltage, fill factor and efficiency. Numerical simulation
shows that the highest efficiency of single-junction CdS/CdTe solar cell equal
to 18.3% is achieved when the CdTe layer thickness is 1000 nm and a CdS layer
is 60 nm. Then, in order to obtain the maximal value of the efficiency, new
tandem multi-junction structure consisting of layers of two solar cells
connected with each other back to back are designed and engineered taking into
account the results obtained for the single-junction solar cells. Numerical
simulations show that its highest efficiency in 31.8% can be obtained when the
thickness of CdS p-layer is equal to 50 nm, and the thickness of the CdS
n-layer is equal to 200 nm, while thicknesses of the CdTe n-layer and CdTe
p-layer are kept fixed and equal to 3000 nm and 1000 nm, respectively.
