Optimization of the MA/FA Ratio in the Structure of Absorber Layers Based on MA(1-x)FAxPbI3 Perovskites for Stable and Efficient Solar Cells

Abstract

Herein, we investigate the mixture of methylammonium lead iodide (MAPbI3) and formamidinium lead iodide (FAPbI3). The perovskite films were coated onto fluorine-doped tin oxide (FTO) glass substrates using a spin-coating method, with the spin-coater set at 4,000 rpm for 20 s. We studied the influence of incorporation in MA(1-x) FA(x)PbI3 films. The crystal structure of the perovskite films was characterized using X-ray diffraction (XRD). Optical properties were assessed using UV-Vis spectroscopy with a spectrophotometer, and photoluminescence (PL) was characterized using a He-Cd Si-CCD laser source and a Hamamatsu detector. Images depicting the characteristic morphology of the films were captured with a scanning electron microscope (SEM). Our measurements reveal that the crystallinity of the MAPbI3 thin film improved with the incorporation of FAPbI3. In the case of 70% FAPbI3, the morphology of the MA30FA70PbI3 mixture also improved, exhibiting a rough surface with pores. The optical properties were enhanced, and the mixed thin film demonstrated better stability compared to pure MAPbI3 and FAPbI3 thin films. These film characteristics indicate that the mixtures are particularly suitable for use in photovoltaic applications.