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.