Modifying The Bottom Interface For Improved Performance Of Perovskite Solar Cells

Abstract

The non-exposed feature of the bottom interface of perovskite solar cells (PSCs) makes direct access to it more challenging, and less attention has been paid to relevant research in the past. Herein, we passivated the bottom interface of perovskite films with ethylammonium bromide (EABr) for inverted PSCs, and the passivation mechanism for the bottom interface is visualized through the solution immersion method to lift off the perovskite layer. The PbI2 residues at the bottom interface, which is the main source of defects and the degradation site of perovskite, are almost eliminated after EABr treatment. It also improved the substrate wettability to facilitate the adhesion and crystallization of the perovskite at the bottom. The bottom surface energy level of the perovskite film is also raised to a level matching that of the hole transport layer it contacts, thus facilitating hole extraction and electron blocking at this interface. The study of charge carrier dynamics further verified the above phenomena. The power conversion efficiency (PCE) of the inverted PSCs reaches 21.06% from 20.41% since all their photovoltaic parameters improved. Our study fully explained the importance of perovskite bottom interface engineering to further improve the performance of PSCs from multiple perspectives such as defect passivation, crystallization, and energy level arrangement, and demonstrated the value of directly characterizing the bottom interface for it.