(A) study on fabrication of roll-to-roll slot die-coated perovskite solar cells via solvent evaporation control

Abstract

Perovskite solar cells (PSCs) are a promising candidate for next-generation flexible solar cells due to their high efficiency and flexibility. However, to commercialize the PSCs, it should be applied the roll to roll (R2R) process, a large-scale and continuous coating process. For the manufacturing of PSCs with roll to roll process, there are some issues to solve. For example, non-uniform surfaces were formed due to slow drying in R2R process, and low efficiency of R2R processed PSC is shown due to usage of one component MAPbI3 materials. In this thesis, we studied the characteristics of PSCs for applying to the R2R systems. First, we introduced an anti-solvent method to R2R process that is widely used in the spin coating process for obtaining the smooth perovskite films. For the process optimization, we control the critical process parameter such as drying conditions and wet thickness of the R2R slot die coating. Also, we suggested the crystal growth mechanisms according to the different process parameters. As a result, we fabricated PSCs which have 9.7 % power conversion efficiency. In addition, we made a process window to obtain uniform thin films according to the drying conditions and the wet coating thickness. Second, for the triple cation PSCs with high efficiency and superior stability, a new DMF:DMSO:ACN solvent system was introduced to fabricate a triple cation PSCs. To get uniform perovskite layers, the evaporation rate was controlled by adding the volatile ACN to conventional nonvolatile DMF:DMSO solvent. In addition, DMSO helped to form the intermediate phase, resulting in large crystals. As a result, we achieved uniform perovskite film with large-sized crystals and the PCE values of PSCs were 13.4 % which comparable to spin-coated PSCs. As knowledge and results of this thesis, it could be helpful for commercialization of PSCs.