Use of Magnetic Fields for Surface Modification of PbI2 Layers to Increase the Performance of Hybrid Perovskite Solar Cells

Abstract

Hybrid perovskite films are prepared via two-step spin coating. The impact of magnetic fields during the spin coating of the PbI2 precursor solution is assessed with atomic force microscopy and scanning electron microscopy of the obtained layers. Deeper and narrower peak–valley–peak formations are obtained in PbI2 films when the magnetic field applied and the spinning direction result in a Lorentz force that pushes the [PbI6]4− ions towards the inner area of the substrate. This produces rougher and more porous PbI2 films with an increased surface area that facilitates the infiltration of the methylammonium iodide and chloride precursor solution, thereby enhancing the formation of perovskite. Increased cell performance and more repeatable results are obtained when the PbI2 film is spin-coated under the influence of a negative magnetic field. Opposite effects are obtained when the direction of the magnetic field, and therefore the Lorentz force, is inverted. This demonstrates that a magnetic field can be used to modify the surface morphology of spin-coated thin films prepared from ionic precursor solutions.