Manipulating the Interfacial Dipole Toward High-Performance Perovskite Solar Cells via Conjugated Organic Ammonium

Surface defect passivation is an important and effective strategy to improve the stability and efficiency of the perovskite solar cells. Here, we develop an organic ammonium molecule with a large π-conjugation, anthracen-2-aminium iodide (AAI), as an efficient surface passivation modulator. Density functional theory (DFT) calculation demonstrates that AAI molecules assembled on the surface of the perovskite in the perpendicular direction and the upright anthracenes form a tight organic layer on the top of the perovskite layer by π–π stacking interactions. This conjugated ammonium could maximize the interfacial dipole and greatly enhance the carrier transfer from the absorber perovskite layer to the hole transport layer without changing the phase of the bulk perovskite layer, as well as improve the energy level misalignment. Therefore, it results in the increased Voc of 1.19 V for the AAI-based device along with a high power conversion efficiency of 24.7% and excellent long-term stability.