Abstract:
CdTe is a very potential binary semiconductor
material for solar photovoltaic application due to its superior
optoelectronic properties. The overall performances of
incorporating Cd1-xZnxS window layer in lieu of CdS layer in
CdTe solar cell were investigated by SCAPS-1D simulator. The
Cd1-xZnxS is an alloy of CdS and ZnS which increase band gap of
window layer from 2.42 eV to 3.7 eV as a function of x (from x=0
to 1). The spectral response of the design Cd1-xZnxS/CdTe cell
improves in blue region which implies the big improvement of
short circuit current density Jsc. In addition, in the traditional
back contact of CdTe cell a small positive conduction band (ΔEC
<0.3 eV) offset is necessary to reduce the forward current J0 as
well as the recombination losses at the back contact. To achieve
this goal a highly doped ZnTe:Cu extra layer was used as an
electron reflector (ER) above back contact. Furthermore, this ER
interface allows electron tunnelling by reducing the barrier
height of the valence band which in turn leads to an
improvement of open circuit voltage and fill factor. The
performance of the proposed cell was examined by varying
thickness and doping concentration of transparent conducting
oxide (TCO) layer, window layer, absorber layer and finally ER
layer. The simulated results of the proposed cell had shown that
the open circuit voltage (Voc) overcame the 1-volt barrier of CdTe
cell with energy conversion efficiencies of 19.93 %.
