SKPM study on organic-inorganic perovskite materials

We report Atomic Force Microscopy (AFM) and Scanning Kelvin Probe Microscopy (SKPM) studies on the surface morphology and surface potential properties of CH 3 NH 3 PbI 3 , CH 3 NH 3 PbI 3 -x Cl x , CH 3 NH 3 PbI 3 -x Br x and CH 3 NH 3 PbBr 3 -x Cl x , respectively. For CH 3 NH 3 PbI 3 rod structure, its surface potential is independent of the precursor concentration, suggesting a robust electronic feature. Surface potential studies of CH 3 NH 3 PbI 3 particle reveal that the Fermi level within CH 3 NH 3 PbI 3 is strongly influenced by the substrate. In the case of CH 3 NH 3 PbI 3 -x Cl x , its surface potential depends on precursor concentrations and we suspect that chlorine concentrated solutions might lead to more chlorine incorporation in the final products, thus lowering its Fermi level. Also, we studied the surface potentials of CH 3 NH 3 PbI 3 -x Br x and CH 3 NH 3 PbBr 3 -x Cl x with specified halide ratios. The surface potential differences between different samples are related to their work function variations. These results are helpful to the understanding of the structural and electronic properties of perovskite materials.