本研究報告了通過旋轉塗佈法和水熱法製備單獨的 p 型和 n 型 BiFeO3 薄膜及其耦合以在 FTO/玻璃基板上形成同質結薄膜。製造了兩種類型的同質結面薄膜：NPB 樣品（NPB3、NPB7 和 NPB10）和 PNB 樣品（PNB3、PNB7 和 PNB10）。 XRD 結果表明，所有樣品均製備了純 BiFeO3 相。 n 型和 p 型 BiFeO3 薄膜分別由奈米顆粒和多面體組成。 Mott-Schottky 測量證實 NB7 和 PB 樣品分別是 n 型和 p 型半導體。還確定了 NB7、PB、NPB7 和 PNB7 的平帶電位和載流子濃度。 NB7 和 PB 的能隙約為 2.2 eV。 n 型和 p 型 BiFeO3 各自的功函數和電離勢分別約為 4.8 和 6 eV，以及大約 5.2 和 5.8 eV。然後從紫外-可見光譜和紫外光電子能譜中獲得接觸前n型和p型BiFeO3的能帶圖。各種複合薄膜的壓電光降解性能優於純n型和p型BiFeO3，NPB7樣品表現出最高的降解速率常數k，約為6.5 x 10-3 min-1，約為23%高於無應力的純 BiFeO3。這些表明了複合材料的同質結面和壓電性的積極影響。誘導的壓電電位分別降低和提高了同質結界面處p型BiFeO3和n型BiFeO3的能帶，導致更高的電子-空穴分離和提高的降解效率。在 NPB7 的三循環性能後，觀察到約 5% 的壓電光降解效率損失並且沒有觀察到結構變化，表明材料的穩定性和可重複使用性。此外，壓電勢分佈的模擬表明，NPB7同質結的感應壓電勢主要由p型BiFeO3在壓應力下貢獻。該分析還闡明了壓電光降解結果。

This study reports the fabrication of individual p-type and n-type BiFeO3 films and their coupling to form homojunction films on FTO/glass substrates through spin coating and hydrothermal method. Two types of homojunctions were fabricated: NPB samples (NPB3, NPB7, and NPB10) and PNB samples (PNB3, PNB7, and PNB10). XRD results revealed that pure BiFeO3 phases were fabricated for all of the samples. The n-type and p-type BiFeO3 films were composed of nanoparticles and polyhedrons, respectively. Mott-Schottky measurement affirmed that the NB7 and PB samples were n-type and p-type semiconductors, respectively. The flat band potential and carrier concentrations for the NB7, PB, NPB7, and PNB7 were also determined. The band gaps of the NB7 and PB were approximately 2.2 eV. The respective work function and ionization potential for the n-type and p-type BiFeO3 were approximately 4.8 and 6 eV, and approximately 5.2 and 5.8 eV, respectively. An energy band diagram of the n-type and p-type BiFeO3 before contact was then obtained from the ultraviolet–visible spectroscopy and ultraviolet photoelectron spectroscopy. The piezo-photodegradation performance for the various composite films was superior to that for the pure n-type and p-type BiFeO3, the NPB7 sample exhibited the highest degradation rate constant k of approximately 6.5 x 10-3 min-1, approximately 23% higher than that for the pure BiFeO3 without stress. These indicated the positive impact of the homojunction and piezoelectricity for the composite. The induced piezopotential lowered and raised the band of the p-type BiFeO3 and the n-type BiFeO3 at the interface of the homojunction, respectively, leading to the higher electron-hole separation and enhanced degradation efficiency. Approximately 5% of piezo-photodegradation efficiency loss and no structure changes were observed after three-cycle performance for the NPB7, indicating the stability and reusability of the material. In addition, the simulation of the piezopotential distribution indicated that the induced piezopotential of the NPB7 homojunction was predominantly contributed by the p-type BiFeO3 under compressive stress. This analysis also elucidated the piezophotodegradation result.

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