Direct Ion-Exchange Method for Preparing a Solution Allowing Spontaneous Perovskite Passivation via Hole Transport Material Deposition

We propose a direct ion-exchange (DI) method for preparing a hole transport material (HTM) solution undergoing spontaneous perovskite passivation via HTM deposition and verify its applicability for the photovoltaic performance enhancement of perovskite solar cells (PSCs). The simple synthesis of a Spiro-OMeTAD HTM solution based on ion exchange via dissolving and mixing multiple solid materials in a chlorobenzene solution produces an HTM solution similar to that obtained with an n-octylammonium bis(trifluoromethanesulfonyl)imide ionic liquid functioning as a spontaneous perovskite passivator. Using the resulting HTM solution, the power conversion efficiency of PSCs was enhanced up to 23.0% without conventional post-passivation processes.