Enhancing the Optoelectronic Properties of Quasi Two‐Dimensional Perovskite by Cesium Iodide Additive

ABSTRACT Due to the numerous grain boundaries and defects in quasi‐two‐dimensional (2D) perovskite films, their non‐radiative recombination increases, which in turn affects the photovoltaic conversion efficiency of solar cells. In this article, we introduce CsI to modify quasi‐2D perovskite thin films, improve their film quality, reduce non‐radiative recombination, and thereby enhance the photoelectric conversion efficiency (PCE) and stability of the device. The results of x‐ray diffraction (XRD) indicate that the introduction of CsI improves the crystallinity of the film and enhances the absorption intensity. Fluorescence spectroscopy shows that cesium iodide entering the 2D perovskite film reduces the non‐radiative recombination of the film. It was found that the introduction of CsI‐modified thin film into solar cells increased the PCE of the device from 9.91% to 12.61% at the optimal concentration. The contact angle test showed that the addition of CsI reduced the hydrophilicity of the film. The stability results of the device indicate that the PCE of the device can still maintain over 90% of the original efficiency at the optimal addition concentration, whereas the reference device can only maintain 20% of the original efficiency. This work provides a reference method for improving the efficiency and stability of quasi‐2D perovskite cells.