| Transparent Conducting Oxides (TCOs) are unique materials with high electrical conductivity and optical transparency, which have been extensively used in optoelectronic devices such as light emitting diodes (LEDs), solar cells, flat-panel displays (FDPs), and smart windows. Currently, tin doped indium oxide (In2O3:Sn, ITO) is the most widely commercially-produced n-type TCO due to its superior properties and industrial performance. However, its application is limited by the rarity and high cost of indium. This has stimulated research for finding alternative new and cheap TCO materials based on more abundant elements. Tin dioxide is a promising alternative candidate, which is a low cost and non-toxic material and also exhibits electrical and optical properties comparable to those of ITO. More recently, SnO2-based TCOs have been attracted considerable attention in experimental and theoretical studies. For example, ATO (antimony-doped SnO2) and FTO (fluorine-doped SnO2) have been developed and widely used. However, conductivity of ATO and FTO is still weak comparable to ITO, so it remains necessary to explore new SnO2-based TCO materials in order to meet future application of TCOs.Recent advances in theoretical methods such as density-functional theory (DFT) provide an extremely valuable tool for predicting structures and properties of a large number of materials for both finite and periodic systems. More interesting, first principles-based calculations can serve as predictive tools to guide the design and development of new materialsIn this paper, we will use the first-principle method design and calculate materials based on SnO2system, our main research focus on the conductive properties of the materials, finally, we will predict the optical properties of the new TCO materials and provide guidance for the future experiments. The main research content and innovative design strategy:(1) Based on the first-principle calculations (GGA-PBE and HSE06), we studied the electronic structure of SnO2, such as the lattice structure, band structure, density of states and effective mass, and verify the correctness of our calculation method.(2) In the monodoping cases, group VA VB, VIB, and VIIA elements are used as the dopants so as to guarantee that the doping system is n-type conductivity and then exhibits high electron mobility. We use GGA-PBE method calculate dopants monodoping SnO2with a wide range of screening. The design principles for SnO2-based TCOs should include three significant properties:(a) high electrical conductivity; (b) high optical transparency (band gaps greater than3.1eV);(c) high chemical/structural stability and convenient synthesis in experiments. In addition, low cost and non-toxicity are also necessary. In first principles-based computer screening, electrical conductivity and optical transparency can be described by effective mass and band gap obtained from electronic structure calculations. Accordingly, the chemical/structural stability and the difficulty of experimental synthesis can be characterized by the binding energy and the formation energy based on electronic structure calculations. In this work, the outcome of the screening includes all already known successful SnO2-based TCOs (ATO, FTO) and also two new ones, iodine-doped SnO2, IOTO; iodine and phosphorus codoped SnO2, IPTO.(3) The screening method is then applied to search the dopants in codoping SnO2based on the prediceted dopants in monodoping cases. In the codoping cases, PTO as a research system,group VB, VIB, and VIIA elements are used as the dopants,the donor-donor combinations are used to guarantee that the doping system is n-type conductivity. Compared to results of monodoping and codoping, fluorine and phosphorus codoped SnO2,(FPTO) has the best conductivity in all candidates, which need to be validated by further experimental investigation.(4) Finally, further research for electronic structure of FPTO material is calculaed by HSE06hybrid functional calculations,and then we make a prediction of the effective mass and optical properties. |
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