Automation of the Antisolvent Method via an Automated Spin-coating System and the Effects of Reduced Surface Roughness and Depth Distribution of Residual PbI2 on Reproducibility

Perovskite solar cells often exhibit performance variability even under identical experimental conditions. One of the reasons of this inconsistency is attributed to manual interventions such as the application of antisolvents. To address these challenges, we develop an automated system to precisely control the solvent dropping and substrate heating processes. Spin coating is performed by using an automated system comprising a robot arm, spin coater, automatic solution dropping part, hot plate, and substrate storage area. Manual fabrication is conducted simultaneously to compare the outcomes. The reproducibility of devices fabricated by using the system and intra- and interbatch consistency are assessed. The automated system considerably diminishes performance fluctuations across batches conducted on different dates from 2.2 to 0.4%. Especially, the automated, uniform application of an antisolvent considerably minimize surface roughness variability in perovskite films. X-ray diffraction analyses further reveal differences between the residual PbI2 contents of perovskite films fabricated via automated and manual methods. Additionally, grazing incidence wide-angle X-ray scattering measurements indicate that the residual PbI2 depth distribution in the perovskite layer was influenced by the antisolvent drop rate and timing. The results suggest that precise control of antisolvent drop rates and drop timings can improve the reproducibility of perovskite solar cells.