Passivating treatment using organic
molecules has become one of
the most efficient means to reduce electronic defects and enhance
perovskite crystallinity for high-performance perovskite solar cells
(PSCs). However, the solvents essentially needed to dissolve the passivating
molecules are rarely concerned during the construction of high-quality
perovskite layers. Here, the role of the passivating solvents in the
secondary growth process and defect passivation of methylammonium
lead iodide (MAPbI3) perovskite films and their influence
on the final device performance are systemically investigated. In
the guanidinium chloride (GACl)-passivated MAPbI3 films
produced with different passivating solvents, we found that the passivating
solvents with poor solubility toward MAPbI3 crystals can
hardly alter the film morphology and the passivation effect of GACl
molecules only works on the upper surface of the photoactive layer.
However, the isopropanol (IPA) capable of partially dissolving the
preformed MAPbI3 crystals contributes to the formation
of excellent polycrystalline perovskite morphologies with remarkably
enhanced grain size and reduced grain boundaries. Consequently, a
maximum power conversion efficiency (PCE) of 18.65% has been realized
for the inverted PSCs fabricated under GACl/IPA passivating treatment
conditions. These results indicate that the solvent used to dissolve
passivators is of great importance in manipulating the MAPbI3 films, providing crucial understanding on the rational selection
of solvents to establish the most effective passivation solutions
for improving the quality of perovskite films and enhancing the PSC
efficiencies.