MAPbBr₃-MAPbI₃ gradient films prepared at room temperature by Powder Aerosol Deposition (PAD) for controlled ion and electron transport

Title data

Xu, Tianshan ; Griesbach, Markus ; Scholz, Till ; Köhler, Anna ; Moos, Ralf:
MAPbBr₃-MAPbI₃ gradient films prepared at room temperature by Powder Aerosol Deposition (PAD) for controlled ion and electron transport.
2025
Event: 8th International Conference on Perovskite Solar Cells and Optoelectronics - PSCO 2025 , 15.9.-18.9.2025 , Perugia, Italy.
(Conference item: Conference , Poster )

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In halide perovskites, the diffusion of ions, driven by an electric field, concentration gradients, or light, usually causes an electric field that impacts the motion of electrons. This coupling of ion and electron transport is undesired, leading, e.g. to hysteresis in solar cell structures due to the much slower ion motion than electron motion. In this study, we report a novel approach to fabricate MAPbBr₃–MAPbI₃ gradient films at room temperature using the Powder Aerosol Deposition method (PAD) [Figure 1], a solvent-free and scalable technique. This method enables the use of mechano-chemically synthesized powders to deposit dense films at room temperature, thereby decoupling the halide synthesis from film formation. The resulting gradient films enable spatially resolved optical and electrical measurements, thus providing deeper insights into ion–electron interactions and field-dependent phenomena in complex perovskite systems. SEM images of the PAD-gradient films show that a dense and nanocrystalline film structure is achieved. EDX mapping reveals a clear vertical distribution of bromide and iodide, indicating the formation of a compositional gradient within the film. The resulting gradient structure enables spatial control over halide composition, leading to tailored band alignment and improved separation of ion and electron transport. We investigated the effects of applying electric fields both along and perpendicular to the compositional gradient, focusing on how electric field orientation influences ionic and electronic transport properties—characterized by impedance spectroscopy— as well as optical behavior, probed by fluorescence lifetime microscopy (FLIM). This work highlights the potential of Powder Aerosol Deposition for engineering perovskite interfaces and advancing the design of high-efficiency, stable perovskite solar cells.