Performance Improvement of Perovskite Solar Cells by Using Ionic Liquid BMIMPF6 as an Interface Modifier

A pristine electron transport layer (ETL) usually delivers relatively low device performance due to high defect density and/or poor contact. Interface modification has been demonstrated to be one of the most effective strategies to passivate the defects and improve the contact. In this study, we employ ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) as an interface modifier between an ETL and perovskite layer. The modified ETL shows enhanced electron conductivity and a more suitable energy level, which facilitate the electron transport. In addition, the modification reduces the electron trap density, which decreases the hysteresis while simultaneously improving the power conversion efficiency of the device from 18.03 to 19.66%.