Organic Salt-Assisted Growth and Orientation of Two-Dimensional Ruddlesden-Popper Perovskites for Efficient Solar Cells

Abstract

Two-dimensional (2D) Ruddlesden-Popper (RP) perovskite solar cells (PSCs) have drawn significant attention due to their appealing environmental stability compared to their three-dimensional (3D) counterparts. However, the relatively low power conversion efficiency (PCE) limits greatly their applications. Here, high photovoltaic performance has been demonstrated for 2D RP perovskite solar cells (PSCs) using 2-thiophenemethylammonium (ThMA) as spacer with nominal n-value of 5. The incorporation of formamidinium (FA) in 2D RP perovskite reduced the bandgap and improved the light absorption ability, resulting in enlarged photocurrent and an increased PCE of 16.18%, which was higher than that of reported analogous methylammonium (MA)-based 2D RP PSC (~15%). A record-high PCE of 19.06% was further demonstrated by using an organic salt assisted crystal growth (OACG) technique, which could induce the crystal growth and orientation, reduce the trap density, suppress the charge recombination loss and tune the surface energy level. More importantly, the devices based on OACG-processed 2D RP perovskite show remarkable environmental stability and thermal stability, for example, the PCE retaining ~96% of its initial value after storage at 80 °C for 576 h, while only ~37% of the original efficiency left for FAPbI 3 -based 3D PSCs.