Optical design of perovskite solar cells for applications in tandem configuration with CuInSe2 bottom cells*

Thin film tandem solar cells consisting of a high bandgap perovskite top cell and a low bandgap thin film bottom cell are expected to reach higher power conversion efficiencies (PCEs) with lower manufacturing cost and environmental impacts than the market-dominant crystalline silicon photovoltaics. There have been several demonstrations of 4-terminal and 2-terminal perovskite tandem devices with CuInGaSe2 (CIGS) or CuInSe2 (CIS) and, similar to the other tandem structures, the optimization of this device relies on optimal choice for the perovskite bandgap and thickness. Therefore, further advancement will be enabled by tuning the perovskite absorber to maximize the photocurrent limited by the current match condition. Here, we model the photocurrent generations in both perovskite and CIS subcells while varying the perovskite layer and estimate the performances of projected tandem devices by considering results of fabricated devices. Our results show that PCEs above 20% can be achieved by perovskite/CIS tandem solar cells for 2- and 4-terminal devices.