Bandgap Engineering of Double Perovskites for One- and Two-photon Water Splitting
- PDF / 1,011,200 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 101 Downloads / 151 Views
Bandgap Engineering of Double Perovskites for One- and Two-photon Water Splitting Ivano E. Castelli1 and Kristian S. Thygesen1 and Karsten W. Jacobsen1 1 Center for Atomic-scale Materials Design, Department of Physics, Technical University of Denmark, Kongens Lyngby, DK-2800, Denmark. ABSTRACT Computational screening is becoming increasingly useful in the search for new materials. We are interested in the design of new semiconductors to be used for light harvesting in a photoelectrochemical cell. In the present paper, we study the double perovskite structures obtained by combining 46 stable cubic perovskites which was found to have a finite bandgap in a previous screening-study.1 The four-metal double perovskite space is too large to be investigated completely. For this reason we propose a method for combining different metals to obtain a desired bandgap. We derive some bandgap design rules on how to combine two cubic perovskites to generate a new combination with a larger or smaller bandgap compared with the constituent structures. Those rules are based on the type of orbitals involved in the conduction bands and on the size of the two cubic bandgaps. We also see that a change in the volume has an effect on the size of the bandgap. In addition, we suggest some new candidate materials that can be used as photocatalysts in one- and two-photon water splitting devices. INTRODUCTION Density Functional Theory (DFT) is a powerful method to investigate structural and electronic properties of materials. The enormous increase of computational power in combination with theory developments, like the implementation of new, more reliable exchangecorrelation functionals, have made it possible to search for new materials using ab-initio quantum mechanical calculations involving several thousands of simulations. Many efforts we have been recently made to design new materials using computational tools, for example screening for organic photovoltaics,2-3 inorganic scintillators4 and bandgap engineering.1,5-7 In previous works,1,6 we addressed one of the most pressing problems of our time, i.e. the development of sustainable energy technology, focusing on the photoelectrochemical conversion of water into hydrogen and oxygen using visible solar light considering both the one- and twophoton water splitting processes. Out of 19000 materials in the cubic perovskite structure, obtained by combining 52 interesting metals with oxygen, nitrogen, sulfur and fluorine, we suggested 20 combinations for one-photon water splitting and 12 additional ones for the twophoton process. In this work, we consider the double perovskite structure for finding new rules to combine metals to obtain the desired bandgap size and to predict new candidates for water splitting. In the previous study we identified 46 stable ABO3 perovskites with a non-vanishing bandgap and here we look at combinations of those in the so-called double perovskite structure shown in Figure 1A. The chemical formula is A1A2B1B2O6; A1 and A2 have an oxygen coordination of 12 and are in gen
Data Loading...
