Chinese researchers reveal mechanism of charge transport performance within perovskite films

HANGZHOU -- A group of Chinese researchers has developed a three-dimensional (3D) electrical imaging method that directly reveals how defect passivation treatment improves the quality of perovskite films and related solar cell performance.

The study was recently published in the journal Newton.

Perovskite solar cells have attracted widespread attention as a low-cost and high-efficiency alternative to conventional silicon photovoltaics. However, defects buried inside perovskite films can impede charge transport, leading to energy loss and reduced operational stability.

Passivation treatments aim to mitigate these defects, but verifying their internal efficacy remains elusive, as most characterization techniques probe only the surface or provide averaged macroscopic information.

To address this challenge, the researchers at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS) employed tomographic conductive atomic force microscopy to visualize current distribution across perovskite films.

The technique works by sequentially removing ultrathin layers of the film while measuring local electrical conductivity at different depths. By stacking these measurements, a 3D map of charge transport within the film is reconstructed with nanoscale resolution.

Using this approach, the researchers characterized the internal electrical behaviors of perovskite films treated with different passivation strategies.

Untreated films exhibited extensive low-conductivity regions that hindered charge transport, whereas bulk passivation significantly reduced these regions, particularly along grain boundaries.

Surface passivation mainly enhanced conductivity near the top interface, which is critical for device integration. Films treated with both bulk and surface passivation demonstrated the most uniform and continuous conductive pathways, with remaining low-conductivity regions confined mainly to the surface.

"These microscopic electrical features closely correlate with the resulting solar cell performance, establishing a direct link between 3D charge transport within the film and overall device efficiency," explained Professor Xiao Chuanxiao, a corresponding author of the study.

By delivering a direct, 3D view of how electrons move through perovskite films, this work offers a powerful tool for evaluating and optimizing passivation strategies. It paves the way for the rational design of higher-quality perovskite materials, enabling more efficient and stable perovskite solar cells.