Formation of DY Center as n-type Limiting Defect in Bi-Doped Hybrid Halide Perovskites

TL;DR

This study investigates the formation of DY centers, a type of defect limiting n-type doping, in Bi-doped hybrid halide perovskites, revealing their dependence on material properties and explaining recent experimental observations.

Contribution

It identifies the formation of DY centers in Bi-doped perovskites and explains their occurrence in MAPbBr3 but not in MAPbI3 through first-principles calculations.

Findings

DY centers form in MAPbBr3 with high Fermi levels

DY centers do not form in MAPbI3 due to lower CBM

Results explain recent experimental observations

Abstract

It is well known that the DX center is a kind of defect that limits the n-type doping in some tetrahedral coordinated semiconductors. It is a deep negatively charged defect complex converted from a nominal shallow donor defect, which can serve as a trap center of electrons, thus is detrimental to the performance of optoelectronic devices. Similar to the DX center, we find that a donor-yielded complex center (DY center) also exists in six-fold coordinated semiconducting materials. For example, Bi is commonly expected as a shallow n-type dopant in perovskite APbX3. However, our first-principles calculations show that the DY center is formed in Bi-doped MAPbBr3 when the Fermi level is high in the gap, but, interestingly, it does not form in MAPbI3. The reason that the DY center is formed in MAPbBr3 instead of MAPbI3 is attributed to the high conduction band minimum (CBM) of MAPbBr3. Our results are able to explain recent puzzling experiment observations and the thorough discussions of the formation and the properties of the DY center in perovskites provide enlightening insights to the defect study in six-fold coordinated semiconductors.