**4.3 Applications in regular or inverted structure perovskite solar cells**

Planer structures are always employed, n-i-p standard structure and p-i-n inverted structure. The researchers used 2D/3D perovskite in these two structures as follows: In 2019, Abbas and his co-workers [95] developed a way to add a 2D-layered perovskite with MAPbI3 bulk 3D-perovskite by a vertically oriented 2D-layered mixed with a bulk 3D-perovskite they select the anilinium ion as the sizeable organic cation. In this research, they used a normal n-i-p structure and recorded an efficiency up to 16%. The planar solar cell heterojunction with ITO/ PEDOT-PSS/perovskite/PCBM/BCP/Ag was fabricated [95]. In 2020, Jia Zhang and Bin Hu recorded a 15.93% efficiency with 2D/3D Pb-Sn alloyed perovskite. They applied the inverted structure p-i-n on their work with the solar cell structure (ITO/ PEDOT:PSS/PEAxMA1xPb0.5Sn0.5I3/PC61BM/PEI/Ag) [96].
