The characterization of defects states and charge injection barriers in perovskite solar cells

The power conversion efficiency of perovskite solar cells has exceeded 22% within a few years. To further optimize their performance, the focus should be on minimizing the defects and barriers in the devices. In this work, Kelvin probe force microscopy (KPFM) together with admittance spectroscopy (AS) is utilized in the characterization of charge injection barriers and defects states in perovskite solar cells. Our measurements indicate that perovskite has a defect level of 0.25 eV above its valance band. In addition, charge injection barriers are present in the interface between electron transporting layer (ETL) and perovskite layer. To improve the performance, passivation technique is needed for the removal of defects and charge injection barriers which could act as recombination centers in perovskite solar cells.