Lead Iodide Thin Films via rf Sputtering

Abstract

Lead iodide (PbI2) is a precursor for the preparation of the organolead iodide perovskite (CH3NH3PbI3), which has been used in the fabrication of highly efficient solar cells. In this work, a novel route for the deposition of PbI2 thin films is performed by rf sputtering a target made from compressed PbI2 powder. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed that the PbI2 films produced were uniform, pinhole-free, polycrystalline, and had low roughness. A small concentration of Pb nanocrystals observed within the films is attributed to differences in the sputtering yield of lead and iodide from the PbI2 target. A dependence of band gap on rf sputtering power was observed, which was associated with a reduction in the concentration of Pb nanocrystals. The PbI2 films were efficiently converted into CH3NH3PbI3 perovskite films through the immersion into a methylammonium iodide (MAI) solution, which also converted the remaining Pb nanocrystals into perovskite. This methodology has the potential to forge the way toward a new method for the fabrication of large-area perovskite solar cells.