Conversion efficiency enhancement of methylammonium lead triiodide perovskite solar cells converted from thermally deposited lead iodide via thin methylammonium iodide interlayer

The thermally deposited thin methylammonium iodide (MAI) interlayer worked as protection layer of poly (3, 4-ethylenedioxythiophene) poly (styrene sulfonate) (PEDOT:PSS) in the thermal deposition of lead iodide (PbI₂). And the thin MAI interlayer could be the MAI supplemental layer during converting the thermally deposited PbI₂ into perovskite. The performances of perovskite solar cells (SCs) converted from thermally deposited PbI₂ were remarkably enhanced by using the thin MAI interlayer on PEDOT:PSS. The short-circuit current density (J_SC), fill factor (FF%), and conversion efficiency (η%) of perovskite SCs converted from thermally deposited PbI₂ increased with the initial increase in thickness of the thin MAI interlayer and then reduced when the thickness of thin MAI interlayer exceeded 2.2 nm. Perovskite SCs converted from thermally deposited PbI₂ with a 2.2 nm-thick thin MAI interlayer obtained the largest J_SC, FF%, and η% at 19.44 mA/cm², 74% and 12.75%, respectively, in our study. And the largest J_SC was more than twice larger than that of perovskite SCs converted from thermally deposited PbI₂ without thin MAI interlayer. Although the perovskite SCs converted from thermally deposited PbI₂ without thin MAI interlayer has η% much less than that of perovskite SCs converted from spin-coated PbI₂. The perovskite SCs converted from thermally deposited PbI₂ with 2.2 nm-thick thin MAI interlayer had an η% of 12.75%, which was larger than that of perovskite SCs converted from spin-coated PbI₂ at 10.57%.