  The most studied perovskite-based solar cells reported up to date contain the
toxic lead in its composition. Photovoltaic research and development towards
non-toxic, lead-free perovskite solar cells are critical to finding
alternatives to reduce human health concerns associated with them.
Bismuth-based perovskite variants, especially in the form of methylammonium
bismuth iodide (MBI), is a good candidate for the non-toxic light absorber.
However, the reported perovskite variant MBI thin flms prepared by the solution
process so far suffers from poor morphology and surface coverage. In this work,
we investigate for the first time the optoelectronic, crystallographic and
morphological properties of MBI thin flms prepared via thermal co-evaporation
of MAI and BiI3. We find by modifying the precursor ratio that the layer with
pure MBI composition lead to uniform, compact and homogeneous layers,
broadening the options of deposition techniques for lead-free based perovskite
solar cells.
