First principles study of native defects in InI

Abstract

Heavy-metal halide semiconductors have attracted much interest recently for their potential applications in radiation detection because the large atomic numbers (high Z) of their constituent elements enable efficient radiation absorption and their large band gaps allow room temperature operation. However, defect properties of these halides and their connection to carrier transport are little known. In this paper, we present first-principles calculations on native defects in InI, which is a promising material for applications in room temperature radiation detection. The important findings are: (1) anion and cation vacancies (Schottky defects) form the dominant low-energy defects that can pin the Fermi level close to midgap, leading to high resistivity that is required for a good radiation detector material; (2) the anion vacancy in InI induces a deep electron trap, which should reduce electron mobility-lifetime product in InI; (3) low diffusion barriers of vacancies could be responsible for the observed polarization phenomenon at room temperature.

Perovskite-inspired materials for photovoltaics and beyond—from design to devices

“…It has been reported that InI can exhibit reasonably long PL lifetime over 6 ns [21] and large mobility-lifetime products corresponding to a diffusion length of around 16 μm [110]. Defect calculations also suggest that the main vacancies and anti-site defects do not have transition levels resonant within the band gap, or have high formation energy transition levels that involve a large gradient change (which would have a low capture cross-section) [238]. However, In is not stable in the +1 oxidation state and tends to oxidize to the +3 oxidation state.…”

Efficient carrier transport in halide perovskites: theoretical perspectives

“…The mixed ionic-covalent character is known to give rise to enhanced Born effective charges (which reects enhanced lattice polarization in response to the displacement of ions) in ferroelectric oxides, such as PbTiO 3 , [34][35][36][37] and in halides containing ns 2 cations, such as Tl, In, Pb, and Bi halides. [19][20][21]38 The Born effective charges for Pb are more than doubled from its nominal ionic charge of +2. The Pb-I 4a bond is aligned with the c axis.…”

Experimental evaluation of indium(i) iodide as a lead-free perovskite-inspired material for photovoltaic applications

“…22,23 Still, the interlayer distances in In I are considerably shorter as compared to the aforementioned binary iodides, which suggests that In I could behave as a quasi-3D material. 24 However, this hypothesis was not supported experimentally: a recent study of the charge distribution in an In I lattice suggested weak interlayer interactions, resembling that in graphite, whereas the charge transport within 2D layers is very efficient. 25 Indeed, the lateral two-terminal devices based on ultrathin b -oriented 2D In I flakes functioned as photodetectors with good characteristics.…”

“…26 However, a previous study suggested that the best device characteristics could be obtained by applying a bias in the vertical direction along the crystallographic b -axis due to high interlayer diffusion barriers preventing migration of In + and I − vacancies. 24…”