This is a SC with a configuration composed of several layers of semicondcutor materials, in which one of each, has a different value of Band Gap, and different spectrum of Absorption, i.e. different ranges of absorbed wavelenght within the EM spectrum.
All this layes must be connected in series, so the yielded voltage is optimized
Dear, Jinan Mahdi .This link will help you in your research: (Reducing internal losses could pave the way to low-cost perovskite-based photovoltaics that match silicon cells’ output.)
For single junction solar cells there are the perovskite solar cells, the organic solar cells. For the multijunction solar cells you can refer to a combination of silicon and perovskite. The silicon acts as the lower bandgap bottom cell and the perovskite services as the widegap top cells.
There are intensive work in the literature about these solar cells.
As matter of example please see the papers in the link:
Article Investigating the performance of formamidinium tin-based per...
andArticle Possible efficiency boosting of non-fullerene acceptor solar...