Nanoscale Characterization of Photocurrent and Photovoltage in Polycrystalline Solar Cells

We investigate the role of grain structures in nanoscalecarrierdynamics of polycrystalline solar cells. By using Kelvin probe forcemicroscopy (KPFM) and near-field scanning photocurrent microscopy(NSPM) techniques, we characterize nanoscopic photovoltage and photocurrentpatterns of inorganic CdTe and organic-inorganic hybrid perovskitesolar cells. For CdTe solar cells, we analyze the nanoscale electricpower patterns that are created by correlating nanoscale photovoltageand photocurrent maps on the same location. Distinct relations betweenthe sample preparation conditions and the nanoscale photovoltaic propertiesof microscopic CdTe grain structures are observed. The same techniquesare applied for characterization of a perovskite solar cell. It isfound that a moderate amount of PbI2 near grain boundariesleads to the enhanced photogenerated carrier collections at grainboundaries. Finally, the capabilities and the limitations of the nanoscaletechniques are discussed.