High‐Rate FA‐Based Co‐Evaporated Perovskites: Understanding Rate Limitations and Practical Considerations to Overcome Their Impact

Abstract Vapor phase deposition methods are readily able to achieve uniform coverage of large‐area substrates and are widely considered promising for industrial‐scale perovskite solar cell fabrication. However, as perovskite‐silicon tandem solar cells approach commercialization, practical considerations of manufacturing throughput come into play. Here, it is shown that the inherent sublimation characteristics of the organic precursor formamidinium iodide (FAI) make increasing the deposition rate of FA‐based co‐evaporated perovskites negatively impact replicability and lead to a substantial decrease in power conversion efficiency (PCE). These losses are linked to reduced film homogeneity and the emergence of carbon‐rich regions within the perovskite layer. To mitigate these rate‐induced effects, two approaches are explored: source layout optimization and material preconditioning. Utilizing dual FAI sources rather than a single FAI source reduces the relative PCE drop from ≈23% _rel to ≈9% _rel at a deposition rate of ≈18 nm min ⁻¹ (14.8% PCE @ maximum power point (MPP)) compared to the baseline rate of 5 nm min ⁻¹ (16.2% PCE @MPP). Alternatively, preconditioning a single FAI source reduces the performance losses from ≈31% _rel to ≈26% _rel at a deposition rate of ≈21 nm min ⁻¹ . These findings underscore the importance of tailored source strategies to enable high‐rate FA‐based co‐evaporated perovskites without compromising device performance.