Title: Shallow halogen vacancies in halide optoelectronic materials

Abstract

Halogen vacancies (V_H) are usually deep color centers (F centers) in halides and can act as major electron traps or recombination centers. The deep V_H contributes to the typically poor carrier transport properties in halides. However, several halides have recently emerged as excellent optoelectronic materials, e.g., CH₃NH₃PbI₃ and TlBr. Both CH₃NH₃PbI₃ and TlBr have been found to have shallow V_H, in contrast to commonly seen deep V_H in halides. In this paper, several halide optoelectronic materials, i.e., CH₃NH₃PbI₃, CH₃NH₃SnI₃ (photovoltaic materials), TlBr, and CsPbBr₃, (gamma-ray detection materials) are studied to understand the material chemistry and structure that determine whether V_H is a shallow or deep defect in a halide material. It is found that crystal structure and chemistry of ns² ions both play important roles in creating shallow V_H in halides such as CH₃NH₃PbI₃, CH₃NH₃SnI₃, and TlBr. The key to identifying halides with shallow V_H is to find the right crystal structures and compounds that suppress cation orbital hybridization at V_H, such as those with long cation-cation distances and low anion coordination numbers, and those with crystal symmetry that prevents strong hybridization of cation dangling bond orbitals at V_H. Furthermore, the results of this paper provide insight and guidance tomore » identifying halides with shallow V_H as good electronic and optoelectronic materials.« less

Authors:

Shi, Hongliang ^[1]; Du, Mao -Hua ^[1]

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division

Publication Date:

Wed Nov 05 00:00:00 EST 2014

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); US Department of Homeland Security (DHS)

OSTI Identifier:

1185671

Alternate Identifier(s):

OSTI ID: 1180339

Grant/Contract Number:  

AC05-00OR22725; HSHQDC-14-R-B0009

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. B, Condensed Matter and Materials Physics

Additional Journal Information:

Journal Volume: 90; Journal Issue: 17; Journal ID: ISSN 1098-0121

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE