Unraveling the Native Conduction of Trichalcogenides and Its Ideal Band Alignment for New Photovoltaic Interfaces

• Published in: Journal of physical chemistry. C 2016-01, Vol.120 (3), p.1390-1399
• Main Authors: Tumelero, Milton A., Faccio, Ricardo, Pasa, Andre A.
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.5b10233

The trichalcogenides Sb2S3, Sb2Se3, Bi2S3, and Bi2Se3 share an orthorhombic crystal structure and have recently been pointed out as promising materials for application in solar energy harvesting, such as photovoltaic solar cells, because of their ultimate structural and electronic/optical properties. In this work, using a first-principles theoretical approach, we investigated the origin of the electrical conduction in bulk systems as well as the energy band alignment in different heterostructures composed of these compounds. In the first part, formation energy and thermodynamic transition energy of native point defects are evaluated. In the second part, surface properties such as free energy and electron affinity were obtained. In the third part, the energy alignments of some possible heterostructures were proposed. The excellent agreement between theoretical results and reported experimental values indicates that these trichalcogenides have their electrical properties ruled by native point defects, mainly antisites. The energy alignment between the trichalcogenides and usual photovoltaic substrates shows that these materials can be successfully applied to the construction of type-II staggered heterojunctions. A last analysis is done by considering only homo- and heterojunction of trichalcogenides, showing that these materials could lead to high-efficiency cells with broad spectral absorption and high conduction/valence band offsets.