Semiconductor heterojunctions are an effective way to achieve efficient photocatalysts, as they can provide an adequate redox potential with visible light excitation. Several works have reported synergistic effects with nanoparticle semiconductor materials. The question is still open for thin film heterojunctions formed by stacked layers, as photocatalysis is considered a surface phenomenon. To investigate if the internal layer really affects or modifies the photocatalytic properties of the external material, we analyze the thin film heterojunction with ZnO and Bi₂O₃ semiconductors deposited by spray pyrolysis in two configurations: substrate/ZnO/Bi₂O₃ and substrate/Bi₂O₃/ZnO. Microstructural analysis was performed to verify the formation of the physical junction of the materials and discard new ternary phases. The photocatalytic activity was analyzed as a function of the thickness of the layers under blue light irradiation. We determined the conduction and valence bands positions, the carrier concentrations, mobilities, Fermi levels, etc. that allowed us to distinguish two reaction mechanisms depending on the configuration. There is a strong compromise between the order and thickness of the layers with the photocatalytic activity. The internal electric field produced in the interface defines the route of the photogenerated charges, and therefore the photocatalytic response. Thus, well-designed thin film heterojunctions can indeed improve the photocatalytic activity of the surface layer.

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薄膜光催化异质结的强厚度依赖性：ZnO-Bi2O3 案例研究

半导体异质结是实现高效光催化剂的有效方法，因为它们可以在可见光激发下提供足够的氧化还原电位。一些研究报告了与纳米粒子半导体材料的协同效应。对于由堆叠层形成的薄膜异质结来说，这个问题仍然悬而未决，因为光催化被认为是一种表面现象。为了研究内层是否真正影响或改变外部材料的光催化性能，我们分析了通过喷雾热解沉积的ZnO 和 Bi ₂ O _{3半导体的薄膜异质结，有两种配置：基板/ZnO/Bi 2} O ₃和基板/Bi ₂ O ₃ /ZnO。进行微观结构分析以验证材料物理连接的形成并丢弃新的三元相。分析了蓝光照射下光催化活性与层厚度的函数关系。我们确定了导带和价带位置、载流子浓度、迁移率、费米能级等，这使我们能够根据配置区分两种反应机制。层的顺序和厚度与光催化活性之间存在强烈的折衷。界面中产生的内部电场定义了光生电荷的路径，从而定义了光催化响应。因此，精心设计的薄膜异质结确实可以提高表面层的光催化活性。