金属氧化物半导体的一项重要参数——带隙——在很大程度上决定了这些材料的光吸收性质和在太阳能转化上的应用价值。目前，在半导体材料的带隙类型（即直接带隙或间接带隙）与晶体结构之间的关系上尚无定论。我们将从半导体物理和结构化学的基本理论出发，经过推导提出一个关于金属氧化物半导体的结构–物性关系的假说：d0金属氧化物半导体的带隙类型与晶体结构中金属多面体的拓扑结构直接相关；作为特例，氧化物半导体中金属的配位环境为共顶点的四面体时一般具有直接带隙，为共顶点的八面体时一般具有间接带隙。我们将总结关于d0金属氧化物的已有结果，并以组成类似而结构不同或结构类似而组成不同的几组d0金属氧化物为例，通过实验测量和理论计算来验证这一假说，还将对假想的一维和二维d0金属氧化物半导体的带隙类型做出预言。本项目的研究成果将有助于回答半导体物理和材料化学领域的一个悬而未决的问题，并为太阳能材料的研发提供有力的理论指导。

An important parameter of semiconducting metal oxides — the band gap — largely determines the light absorption properties of these materials and their applicability in the conversion and utilization of solar energy. So far there has been no generally accepted rule or trend that explicitly relates the type of band gap (i.e., a direct or indirect band gap) and the crystal structure of a given semiconductor. Based on the fundamental theories of semiconductor physics and structural chemistry, this project will go through derivations and arrives at a hypothesis regarding the structure–property relationship of semiconducting d0 metal oxides: the type of band gap of a semiconducting d0 metal oxide is directly related to the structural topology of the metal polyhedra in the compound; as two specific examples, semiconducting oxides in which the coordination environment of the d0 metal is corner-sharing tetrahedra usually have direct band gaps, whereas a coordination environment of corner-sharing octahedra usually lead to indirect band gaps. In addition to a comprehensive summary on the existing results of the band gaps and crystal topologies of semiconducting d0 metal oxides, this project will 1) highlight several pairs of d0 metal oxides with similar elemental compositions but different structures, or the other way around; 2) examine the structure–property relationship on these example systems, using both experimental measurements and theoretical calculations; and 3) offer predictions about the types of band gaps of hypothetical one- and two-dimensional semiconducting d0 metal oxides. The research outcomes from this project application are expected to contribute to the solution of a long-standing problem in the areas of semiconductor physics and materials chemistry, and to provide deep insights into the principles underlying the development of high-performance solar energy materials.