Atomic and electronic structure of Lomer dislocations at CdTe bicrystal interface

Abstract

Extended defects are of considerable importance in determining the electronic properties of semiconductors, especially in photovoltaics (PVs), due to their effects on electron-hole recombination. We employ model systems to study the effects of dislocations in CdTe by constructing grain boundaries using wafer bonding. Atomic-resolution scanning transmission electron microscopy (STEM) of a [1–10]/(110) 4.8° tilt grain boundary reveals that the interface is composed of three distinct types of Lomer dislocations. Geometrical phase analysis is used to map strain fields, while STEM and density functional theory (DFT) modeling determine the atomic structure at the interface. The electronic structure of the dislocation cores calculated using DFT shows significant mid-gap states and different charge-channeling tendencies. Cl-doping is shown to reduce the midgap states, while maintaining the charge separation effects. This report offers novel avenues for exploring grain boundary effects in CdTe-based solar cells by fabricating controlled bicrystal interfaces and systematic atomic-scale analysis.

Slow wave contraction frequency plateaux in the small intestine are composed of discrete waves of interval increase associated with dislocations

“…Both contraction and crystal dislocations are generated where there is a break or mismatch in some property. Crystal dislocations repeat at its surface or the interface of a composite crystal (Liu et al., ; Sun et al., ; Zhang et al., ; Zhu, Li, Samanta, Leach, & Gall, ). In the intestine, the interface is a point of low coupling at a frequency step.…”

“…Crystal dislocations repeat at its surface or the interface of a composite crystal (Liu et al, 2013;Sun et al, 2016;Zhang et al, 2015;Zhu, Li, Samanta, Leach, & Gall, 2008). In the intestine, the interface is a point of low coupling at a frequency step.…”

Strain Mapping of CdTe Grains in Photovoltaic Devices

“…Strain was observed to contribute to band tails, and recrystallization during CdCl 2 treatments has been shown to relax this strain [10]. At the sub-nanometer scale, local lattice distortions, also called microscopic strain, have been studied at interfaces, and individual defects have been observed using transmission electron microscopes (TEM) [11], [12]. In conjunction with density functional theory calculations, lattice distortions at dislocations were shown to produce recombination-active midgap states that Cl can help to mitigate [12].…”

“…At the sub-nanometer scale, local lattice distortions, also called microscopic strain, have been studied at interfaces, and individual defects have been observed using transmission electron microscopes (TEM) [11], [12]. In conjunction with density functional theory calculations, lattice distortions at dislocations were shown to produce recombination-active midgap states that Cl can help to mitigate [12]. Within large grains of very thick (> 200 µm) CdTe material, non-uniformities have been examined using a combination of electron backscattered diffraction (EBSD), electron-beam induced current (EBIC), cathodo-luminescence (CL), and Laue X-ray diffraction.…”

GaAs1-xBix growth on Ge: anti-phase domains, ordering, and exciton localization

“…An attendant challenge for the bismide-based PV development is its growth on Ge substrates, as one is faced with the epitaxy of a polar material on a non-polar substrate. Mixed nucleation of group-III and V elements and random surface steps on the substrate can produce anti-phase domains (APD), which degrade device performance [35][36][37] . As of this writing, the attempt to grow GaAs 1-x Bi x on Ge substrates, to the best of our knowledge, was made only once 38 .…”