Design of Efficient Inverted NiOX‐Based Three‐Terminal Back‐Contact All Perovskite Tandem Solar Cells

Abstract The development of efficient all perovskite tandem solar cells has faced challenges related to current matching and optical losses. In this work, a design of a non‐coplanar three‐terminal (3T) all perovskite tandem solar cell is presented, which consists of a p‐i‐n inverted NiO X ‐based CsPbI 2 Br perovskite top cell, and a FA 0.6 MA 0.4 Sn 0.5 Pb 0.5 I 3 perovskite bottom cell with back‐contact (BC) device structure. It effectively mitigated the optical losses introduced in non‐absorbing layers and resulted in a 2.9% absolute efficiency improvement compared to that of planar sandwich‐type 3T tandems. Both optical and electrical characteristics of the multi‐terminal tandem cells are investigated. Then, it is focused on understanding the impact of top cell thickness on overall non‐coplanar BC 3T‐tandem performance, considering low‐energy photon optical reflection and carrier transport distance. Following optimizations of energy level and device structure, an efficiency of 32.16% is achieved, with non‐coplanar BC 3T device architecture: top cell consisting of hole extraction layer (ITO/NiOx), CsPbI 2 Br absorber layer, and electron extraction layer (ZnO/FA 0.6 MA 0.4 Sn 0.5 Pb 0.5 I 3 /SnO 2 /Ag); and bottom cell (Ni/NiOx/FA 0.6 MA 0.4 Sn 0.5 Pb 0.5 I 3 /SnO 2 /Ag); bottom perovskite layer has two functions, one is electron transport layer for top cell, and the other is low‐energy photon absorption layer in bottom cell. It provides insight and a promising pathway for manufacturing high‐efficient all perovskite tandem solar cells.