Optimization of Deposition and Properties of Printed Complex-Composition Perovskite Films for Flexible Solar Cells

Scalable deposition of high-quality perovskite films is a key challenge for the commercialization of flexible perovskite solar cells. In this work, the deposition process and material properties of printed mixed-cation, mixed-halide perovskite films with the composition Cs0.175FA0.75MA0.075Pb(I0.88Br0.12)3 were systematically optimized using slot-die printing techniques. The influence of key printing parameters, including ink flow rate, coating speed, and substrate temperature, on film thickness, morphology, crystallization behavior, and optical properties was investigated. Optimized conditions enabled the formation of uniform perovskite layers with a thickness of 300–400 nm, a dense microstructure, and strong optical absorption with a bandgap of approximately 1.55 eV. The effects of solvent engineering and crystallization additives were further evaluated. While the pristine DMSO-based formulation provided structurally high-quality films, the incorporation of 5 mol% methylammonium chloride (MACl) significantly improved the film morphology, grain connectivity, and reproducibility without altering phase purity. Consequently, printed flexible perovskite solar cells fabricated with MACl exhibited enhanced short-circuit current density, fill factor, and power conversion efficiency (PCE), reaching a best PCE of 9.72%. These results demonstrate an effective strategy for controlling perovskite film formation in fully printed flexible devices and highlight the potential of MACl-assisted slot-die printing for flexible perovskite photovoltaics.