Assessing Carrier Mobility, Dopability, and Defect Tolerance in the Chalcogenide Perovskite BaZrS3

The chalcogenide perovskite <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:msub><a:mrow><a:mi>Ba</a:mi><a:mi>Zr</a:mi><a:mi mathvariant="normal">S</a:mi></a:mrow><a:mn>3</a:mn></a:msub></a:math> has attracted much attention as a promising solar absorber for thin-film photovoltaics. Here we use first-principles calculations to evaluate its carrier transport and defect properties. We find that <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><e:msub><e:mrow><e:mi>Ba</e:mi><e:mi>Zr</e:mi><e:mi mathvariant="normal">S</e:mi></e:mrow><e:mn>3</e:mn></e:msub></e:math> has a phonon-limited electron mobility of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><i:mn>37</i:mn><i:mspace width="0.2em"/><i:msup><i:mi>cm</i:mi><i:mn>2</i:mn></i:msup><i:mo>/</i:mo></i:math>V s, which is comparable to that in halide perovskites, but lower hole mobility of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><m:mn>11</m:mn><m:mspace width="0.2em"/><m:msup><m:mi>cm</m:mi><m:mn>2</m:mn></m:msup><m:mo>/</m:mo></m:math>V s. The defect computations indicate that <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><q:msub><q:mrow><q:mi>Ba</q:mi><q:mi>Zr</q:mi><q:mi mathvariant="normal">S</q:mi></q:mrow><q:mn>3</q:mn></q:msub></q:math> is intrinsically <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><u:mi>n</u:mi></u:math>-type due to shallow sulfur vacancies, but that strong compensation by sulfur vacancies will prevent attempts to make it <x:math xmlns:x="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><x:mi>p</x:mi></x:math>-type. We also establish that <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><ab:msub><ab:mrow><ab:mi>Ba</ab:mi><ab:mi>Zr</ab:mi><ab:mi mathvariant="normal">S</ab:mi></ab:mrow><ab:mn>3</ab:mn></ab:msub></ab:math> shows some degree of defect tolerance, presenting only few low formation energy, deep intrinsic defects. Among the deep defects, sulfur interstitials are the dominant nonradiative recombination centers but exhibit a moderate capture coefficient. Our work highlights the material’s intrinsic limitations in carrier mobility and <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><eb:mi>p</eb:mi></eb:math>-type doping, and suggests focusing on suppressing the formation of sulfur interstitials to achieve longer carrier lifetime.