First-principles study of band alignments in the p-type hosts BaM₂X₂(M= Cu, Ag;X= S, Se)

Abstract

Abstract. The electronic structures of four semiconductor compounds BaCu 2 S 2 , BaCu 2 Se 2 , BaAg 2 S 2 , and BaAg 2 Se 2 are studied by density functional theory using both semi-local and hybrid functionals. The ionization energies and electron affinities were determined by aligning the electronic states with the vacuum level by calculating the electrostatic profile within a supercell slab model. The ionization energy and electron affinity of the compounds were calculated using the Heyd-Scuseria-Ernzerhof (HSE) functionals and range from 4.5 to 5.4 eV and 3.1 to 3.4 eV, respectively. The replacement of Cu by Ag slightly increases the ionization energy and electron affinity, while the replacement of S by Se decreases the ionization energy but slightly increases the electron affinity. Overall, the low ionization energies and small electron affinities suggest that these compounds possess good p-type doping propensities. The band gaps are somewhat small to be ideal candidates for transparent semiconducting behavior. The replacement of Cu with Ag in the barium sulfide compounds can increase the band gap from 1.62 eV to 2.01 eV.

Properties of Novel Non-Silicon Materials for Photovoltaic Applications: A First-Principle Insight

“…Thus, Ag 2 BaS 2 is a direct band gap semiconductor with a band gap of 1.95 eV. Note that our direct band gap value of 1.95 eV calculated with HSE06 closely matches the previous HSE06 band gap value of 2.01 eV [ 34 ] calculated by Aditi Krishnapriyan et al To the best of our knowledge, no experimental study has been previously reported on Ag 2 BaS 2 . From Figure 2 b and the Figure S4 of Supplementary Materials , the valence band maximum is derived from S-p states and conduction band derived from Ag-s states.…”

High-throughput search of ternary chalcogenides for p-type transparent electrodes

“…However, this strategy looks appealing as the p states of the chalcogen atoms are usually higher and therefore make the compound more prone to be p -doped. Recent calculations suggest that this is the case for Ba(Cu, Ag) 2 (S, Se) 2 compounds36.…”

BaCu2Se2 based compounds as promising thermoelectric materials

“…The crystal structure and transport properties of BaCu 2 Ch 2 (Ch = S, Se and Te) have been studied by few groups to date. [19][20][21][22][23][24][25][26] For Ch = S and Se, two structuretypes can be stabilized: the orthorhombic BaCu 2 S 2 -type and the tetragonal ThCr 2 Si 2 -type. [20][21][22][23] Only the BaCu 2 S 2 structure has been reported for BaCu 2 Te 2 .…”