Two-Step Processed Dion–Jacobson Perovskite for Enhancement of Solar Cell Efficiency and Stability

In this work, we demonstrate that the HTI (HTI = histammonium iodide) dication was incorporated into the PbI 2 precursor solution to induce the preferred vertical orientation of the 2D Dion–Jacobson (DJ) perovskite film using a two-step deposition. 2D DJ (HTI) (FA) x (MA) 1– x Pb n I 3 n +1 (FA = formamidinium, MA = methylammonium) films show a significantly improved film quality with enlarged grain sizes and vertical orientation to the substrate. Moreover, perovskite films prepared from the HTI embedded PbI 2 layer also exhibit greatly reduced film decomposition from oxygen and humidity in ambient air conditions. As a result, the champion device shows a high power conversion efficiency (PCE) of 13.06%, in contrast to 7.98% for the 3D (FA) x (MA) 1– x PbI 3 perovskite device without HTI dication. The 2D DJ (HTI) (FA) x (MA) 1– x Pb n I 3 n +1 devices show enhanced stability, maintaining 72% of their initial PCE after 2000 h in ambient air conditions (relative humidity 35–50%). However, the 3D (FA) x (MA) 1– x PbI 3 perovskite device dropped to 24% of its PCE within 2000 h. Our results suggest that the precursor engineering containing 2D perovskite organic spacer in a two-step process is a potential approach toward further improving the PCE and stability of the 2D DJ perovskite solar cell.