Efficient 2-Terminal All-Perovskite Tandem Solar Cells by Multisource Evaporation

The rapid screen of perovskite solar cells optimization based on solution-processed methods have achieved historical successfully. The next stage of technology development is to transfer from the lab research to fab production lines. Therefore, another deposition route for scalability and modularity needs to be studied. Our work employs a novel dual-interface treatment to maximize the performance of evaporated perovskite devices, which show great promise when implemented into tandem architectures. We employ a 4-source vacuum deposition method to demonstrate perovskites of the tunable bandgap. Engineering the device architecture via the use of a MeO-2PACz layer as HTM demonstrates a 20.7% PCE in a 1.62 eV bandgap perovskite solar cell, which is among the highest performance in a multisource evaporated system. The use of several sources allows precise control over the halide content in the perovskite composition, which is crucial to enlarge its bandgap and make it relevant for widegap subcells for tandem architectures. Halide segregation is a key factor to consider when designing widegap perovskites and we find that a FA_0.7Cs_0.3Pb(I_0.66Br_0.34)₃ film with a 1.77 eV shows great phase stability under light-soaking, though devices display suboptimal voltages. In order to minimize non-radiative losses, we introduce a surface treatment to passivate the evaporated perovskite that translates into 17.8 % PCE devices with a remarkable Voc of up to 1.26 V, which is among the best in evaporated perovskite solar cells. This method is versatile and reproducible, and we extend it to Pb/Sn-based narrow gap perovskite solar cells reaching a Voc of 0.86 V. Incorporating the narrowgap and widegap perovskite building blocks into a 2-terminal tandem solar cell, we obtain a PCE of 24.1% with a promising Voc of up to 2.06 V, which is unprecedented for a system where either of the subcells is deposited by dry methods. This result represents a major step forward in the realization of third-generation multijunction solar cells of superior performance. Our work opens a myriad of possibilities benefiting from the intrinsically scalable, conformal, and reproducible character of vacuum deposition methods, opening the path to the integration of advanced photonic strategies to push perovskite photovoltaics to their limits.