3D nanoscale imaging reveals charge flow in perovskite solar cells

Researchers at the Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences, have developed a novel three-dimensional electrical imaging technique using tomographic conductive atomic force microscopy (TC-AFM) to directly observe charge transport within perovskite solar cell films at the nanoscale. This method sequentially removes ultrathin layers from the film while measuring local electrical conductivity, enabling reconstruction of a 3D map of charge flow. This approach addresses a key challenge in perovskite photovoltaics: internal microscopic defects that disrupt charge transport, reduce efficiency, and compromise long-term stability, which traditional diagnostic tools fail to fully capture. Applying TC-AFM, the researchers compared untreated films with those treated by bulk and surface passivation strategies designed to mitigate defects. Untreated films showed extensive low-conductivity regions, especially along grain boundaries, while bulk passivation significantly reduced these resistive areas throughout the film interior. Surface passivation mainly improved conductivity near the top interface, important for electrode