###### 1 Introduction  
With the decrease in fossil fuels, green and renewable solar energy has become an important part of the energy for human use. In recent years, organic-inorganic hybrid chalcogenide solar cells have become a hot research topic [1; 2; 3; 4]. However, the high cost, low stability, and environmental pollution due to their lead content are non-negligible problems. Typical inorganic oxide chalcogenide ferroelectric materials have the problems of too wide a bandgap to match the solar spectrum and a more complicated preparation process [5]. Therefore, in this paper, a novel organic-inorganic hybrid molecular ferroelectric material [C6N2H18]Bi15 (HDA-Bi15) was chosen, which not only has the narrowest bandgap of 1.89 eV of current molecular ferroelectric materials and can absorb visible light in the range of 380-660 nm, but also has good ferroelectricity, representing a nonpolluting, low-cost, and stable ferroelectric photovoltaic material [6]. A high-quality ferroelectric film is a prerequisite for the preparation of high-performance ferroelectric solar cells, which requires a large grain size, good crystallinity, and a flat and dense film structure [7]. Currently, the recognized bandgap of the light-absorbing layer of photovoltaic devices is in the range of 1.4-1.5 eV [8], and regulating the forbidden bandwidth of ferroelectric materials and preserving their good ferroelectricity are the focus of research. Elemental substitution and material mixing have been favored by researchers as frequently used means in materials research, usually to change the forbidden bandwidth of materials or to enhance the quality of thin films [9; 10; 11; 12]. [PERSON] investigated the modulation of the electronic structure of the two-dimensional ferroelectric semiconductor \(\alpha\)-In\({}_{2}\)Se\({}_{3}\) by alternative doping of a single main group element using a first-principles calculation system based on density generalized theory. It was proposed that the nonvolatile regulation of the electronic structure of the system by the external electric field is achieved by the asymmetric doping of two In atomic layers with different coordination environments present in \(\alpha\)-In\({}_{2}\)Se\({}_{3}\) and the interchangeable properties of the coordination environments of the two In atomic layers corresponding to their ferroelectric flipping [13]. [PERSON] prepared La-doped Bi\({}_{4}\)Ti\({}_{3}\)O\({}_{12}\) ferroelectric thin films using a sol-gel method to study the effects of different La doping amounts on the microstructure and photoelectric properties of Bi\({}_{4}\)Ti\({}_{3}\)O\({}_{12}\) ferroelectric thin films. The results showed that, with the increase in La element doping, the diffraction peak gradually shifted to a higher angle, the grain size gradually decreased, the absorption edge was blue-shifted, and the forbidden bandwidth slightly increased. The photoelectric response of the La-doped Bi\({}_{4}\)Ti\({}_{3}\)O\({}_{12}\) films was significantly better than that of Bi\({}_{4}\)Ti\({}_{3}\)O\({}_{12}\)[14]. The Fe-doped barium titanate BaTi\({}_{1-x}\)Fe\({}_{x}\)O\({}_{3}\) (0.10 \(\leq\) x \(\leq\) 0.60) samples were prepared using a high-temperature solid-phase reaction method, and their structural, ferroelectric, and magnetic properties were investigated by [PERSON] et al. The BaTi\({}_{1-x}\)Fe\({}_{x}\)O\({}_{3}\) material has both ferroelectric and ferromagnetic properties at room temperature. With the increase in Fe doping from 10% to 60%, the magnetic moment generated by a single Fe ion in the material increased from 0.70 uB to 1.55 uB [15].