## 4 Conclusions  
In summary, before polarization, the chlorobenzene-optimized devices showed different degrees of improvement in V\({}_{\rm{oc}}\) and J\({}_{\rm{sc}}\), regardless of forward or reverse sweep, which also led to a 152% improvement in the PCE of the devices compared to the unoptimized ones. The devices before and after chlorobenzene optimization showed an increase in J\({}_{\rm{sc}}\) and iron as a whole under different voltage polarizations, except for the V\({}_{\rm{oc}}\), which did not change significantly, and the PCE was significantly improved. Although the maximum PCE with a value of 0.112% was obtained for the unoptimized device under 1.2 volts polarization, the optimized device showed a more stable performance change during polarization. The reason for the improved device performance due to polarization can also be attributed to the synergistic effect of the depolarizing electric field of the ferroelectric photoabsorption layer and the electric field built into the P-N junction. At present, it seems that ferroelectric materials have not yet become the mainstream of the solar cell photoabsorption layer, but we believe that with the unremitting efforts of researchers, ferroelectric photovoltaic cells are expected to become the best candidate for the next generation of solar cells.  
The following are available online at [[https://www.mdpi.com/article/10.3390/app112110494/s1](https://www.mdpi.com/article/10.3390/app112110494/s1)]([https://www.mdpi.com/article/10.3390/app112110494/s1](https://www.mdpi.com/article/10.3390/app112110494/s1)), Figure S1: X-ray diffraction spectra of organic-inorganic hybrid ferroelectric materials, Figure S2. Ultraviolet-visible light (UV-vis) absorption spectra and photoemission spectra (PL) of organic-inorganic hybrid ferroelectric films, Figure S3. Ultraviolet Photoelectron Spectroscopy (UPS) of Organic-inorganic Hybrid Ferroelectric Material HDA-BiI5, Figure S4. J-V curves of ITO/NiO/x/HDA-BiI5/PCBM/Ag structure devices after different constant voltage polarization. (a) 0.6 V, (b) 0.8 V, (c) 1.0 V, (d) 1.2 V, Figure S5. J-V curves of the optimized device after different voltage polarization. (a) 0.6 V, (b) 0.8 V, (c) 1.0 V, (d) 1.2 V, Figure S6. The vertical PFM phase angles of ferroelectric films are (a) \(-\)10 V, (b) 10 V, (c) \(-\)10 V and the horizontal PFM phase angles are (d) \(-\)10 V, (e) 10 V, (f) \(-\)10 V.  
Conceptualization, X.W. and X.Z.; methodology, Z.Z.; validation, C.Z., Y.W. and X.L.; formal analysis, B.R.; investigation, K.S.; resources, J.C.; data curation, [PERSON]; writing--original draft preparation, [PERSON]; writing--review and editing, [PERSON]; visualization, [PERSON]; supervision, [PERSON]; project administration, [PERSON]; funding acquisition, [PERSON] All authors have read and agreed to the published version of the manuscript.  
This research was funded by the NATIONAL NATURAL SCIENCE FOUNDATION OF CHINA, grant number 61875186 and 61901009. The APC was funded by State Key Laboratory of  
Figure 6: Schematic diagrams of (HDA-BiI5)-based ferroelectric solar cells under different conditions: (**a**) no polarization, and (**b**) polarization.  
Advanced Optical Communication Systems Networks of China (2021 GZKF002) and Beijing Key Laboratory for Sensors of BISTU (No. 2019 CGKF007).  
**Data Availability Statement**: Not applicable.  
**Acknowledgments**: This work was supported by the National Natural Science Foundation of China (No. 61875186 and No. 61901009), State Key Laboratory of Advanced Optical Communication Systems Networks of China (2021 GZKF002) and Beijing Key Laboratory for Sensors of BISTU (No. 2019 CGKF007).  
**Conflicts of Interest**: The authors declare no conflict of interest.