  In this article, we demonstrate the design and simulation of a
highly-efficient n-CdS/p-CIGS/p+-CGS dual heterojunction solar cell. The
simulation was performed using SCAPS-1D software with reported experimental
physical parameters. The simulation performance of our proposed design arises
47% with Voc=0.98 V, Jsc=59.94 mA/cm2 and FF=80.07%, respectively. The high
short circuit current and hence the high efficiency is predominantly originated
from the longer wavelength absorption of photon through a tail-states-assisted
two-step upconversion in dual heterojunction (DH) and thus reaches the SQ
detailed balance limit of DH solar cell.
