Abstract
Halogen vacancies () are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., and TlBr. Both and TlBr have been found to have shallow , in contrast to commonly seen deep in halides. In this paper, several halide optoelectronic materials, i.e., , (photovoltaic materials), TlBr, and (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ions both play important roles in creating shallow in halides such as , , and TlBr. The key to identifying halides with shallow is to find the right crystal structures and compounds that suppress cation orbital hybridization at , such as those with large cation-cation distances and low anion coordination numbers and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at . The results of this paper provide insight and guidance to identifying halides with shallow as good electronic and optoelectronic materials.
- Received 3 September 2014
- Revised 12 October 2014
DOI:https://doi.org/10.1103/PhysRevB.90.174103
©2014 American Physical Society