Hydrogen states in mixed-cation CuIn(1−x)GaxSe2 chalcopyrite alloys: a combined study by first-principles density-functional calculations and muon-spin spectroscopy

• Autor(a) principal: Marinopoulos, A. G.
• Data de Publicação: 2021
• Outros Autores: Vilão, R. C., Alberto, H. V., Ribeiro, E. F. M., Gil, J. M., Mengyan, P. W., Goeks, M. R., Kauk-Kuusik, M., Lord, J. S.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10316/96817; https://doi.org/10.1080/14786435.2021.1972178
• topic: Chalcopyrite solar cells; ab initio calculations; Hydrogen; Muon spectroscopy

First-principles calculations were performed jointly with muon-spin (µSR) spectroscopy experiments in order to examine the electrical activity of hydrogen in mixed-cation chalcopyrite Cu(In1−x,Gax)Se2 (CIGS) alloys and other related compounds commonly used as absorbers in solar-cell technology. The study targeted the range of Ga concentrations most relevant in typical solar cells. By means of a hybridfunctional approach the charge-transition levels of hydrogen were determined and the evolution of the defect pinning level, E(+/–), was monitored as a function of the Ga content. The use of E(+/–) as a metric of the charge-neutrality level allowed the alignment of band structures, thus providing the band offsets between the CuInSe2 compound and the CIGS alloys. The µSR measurements in both thin-film and bulk CIGS materials confirmed that the positively-charged state is the thermodynamically stable configuration of hydrogen for p-type conditions. The interpretation of the µSR data further addressed the existence of a metastable quasi-atomic neutral configuration that was resolved from the calculations and led to a formation model for muon implantation.