Pulsed Spray Pyrolysis for High-Quality Bismuth Ferrite Thin Films: Bi Content Enabled Tuning of Photoresponse, Ferroelectric Domains, and Charge Separation for Energy Harvesting Applications

High-quality bismuth ferrite (BFO) thin films were prepared by using the pulsed spray pyrolysis technique with various bismuth-to-iron ratios. Our optimized pulsed deposition approach yielded dense, device-quality films suitable for large-scale applications. Morphological analysis confirmed the superior quality of the films produced. The bismuth content in the BFO significantly alters the ferroelectric polarization in the material as well as the photoresponse from the material. The Bi content variation results in the coexistence of Fe³⁺ and Fe²⁺ states, as confirmed by X-ray photoelectron spectroscopy (XPS), which has a significant impact on the material’s polarization. The 5 at % Bi-rich film exhibits larger ferroelectric domains compared to the stoichiometric BFO sample, with a transient responsivity of 0.173 mA/W. Furthermore, the fabrication of a single-layer device and the assessment of a suitable electrode for charge carrier separation were studied. The asymmetric electrode configuration enhanced the photoresponse of the device. The study highlights the potential of BFO to be incorporated into the perovskite solar cell device structure with Bi content playing a crucial role in controlling the functional properties of BFO.