Bismuth vanadate is a promising photoanode for solar-to-fuel photocatalytic applications, and it has been extensively studied in recent years. However, the microscopic mechanism underlying the observed changes in electronic conductivity due to oxygen vacancies and nitrogen dopants remains unclear. Here, we combine electronic structure calculations at the hybrid density functional theory (DFT) level with constrained DFT, and we elucidate the role of defects in enhancing the transport properties of the material. We show that at low temperature, oxygen vacancies give rise to deep levels within the fundamental gap of BVO; however even as deep levels, oxygen vacancies can act as effective n-dopants and polaronic charge carriers, due to their favorable position in energy relative to polarons in the pristine bulk. In addition, we show that N atoms can be easily introduced in n-doped BiVO₄ and that the presence of substitutional nitrogen affects the formation energy of polarons, effectively contributing to an increase of the carrier mobility in the material. Our results reconcile apparently conflicting experiments and they may be generalized to other transition metal oxides, thus providing a foundation for polaronic defect engineering in photoanodes for water photocatalysis.

中文翻译：

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点缺陷在增强BiVO ₄电导率中的作用

钒酸铋是一种有前途的光阳极，可用于太阳能到燃料的光催化应用，近年来已进行了广泛的研究。然而，由于氧空位和氮掺杂而导致的电导率变化的微观机理尚不清楚。在这里，我们将混合密度泛函理论（DFT）级别的电子结构计算与受约束的DFT结合起来，并阐明了缺陷在增强材料的传输性能中的作用。我们表明，在低温下，氧空位会在BVO的基本缺口内产生较深的水平；然而，即使深层次，氧空位可以作为有效ñ-掺杂剂和极化子载流子，因为它们在能量上相对于原始块中的极化子处于有利位置。另外，我们表明N原子可以容易地引入到n掺杂的BiVO _4中，并且取代氮的存在影响极化子的形成能，有效地促进了材料中载流子迁移率的增加。我们的结果调和了明显矛盾的实验，它们可能会推广到其他过渡金属氧化物，从而为用于水光催化的光阳极中的极化子缺陷工程提供基础。