Stabilizing the Ag Electrode and Reducing J-V Hysteresis through Suppression of Iodide Migration in Perovskite Solar Cells.

Hysteresis and stability issues in perovskite solar cell (PSCs) hinder their commercialization. Here, we report an effective and reproducible approach for enhancing the stability of and suppressing the hysteresis in PSCs by incorporating a small quantity of two-dimensional (2D) PEAPbI [PEA = CH(CH)NH] in three-dimensional (3D) MAPbI [MA = CHNH ] [denoted as (PEAPbI)(MAPbI)], where the perovskite films were fabricated by the Lewis acid-base adduct method. A nanolaminate structure comprising layered MAPbI nanobricks was created in the presence of 2D PEAPbI. For x = 0.017, a power conversion efficiency (PCE) of as high as 19.8% was achieved, which was comparable to the 20.0% PCE of a MAPbI-based cell. Density functional theory (DFT) calculations confirmed that iodide migration was suppressed in the presence of the 2D perovskite as a result of a higher activation energy, which was responsible for the significant reduction in hysteresis and the improved chemical stability against a Ag electrode as compared to the corresponding characteristics of its pristine MAPbI counterpart. An unencapsulated MAPbI-based device retained less than 55% of its initial PCE in a 35-day aging test, whereas a (PEAPbI)(MAPbI)-based device without encapsulation exhibited a promising long-term stability, retaining over 90% of its initial PCE after 42 days.