Tuning the Band Gap in the Halide Perovskite CsPbBr3 Through Sr Substitution

23 May 2022, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The ability to continuously tune the band gap of a semiconductor allows its optical properties to be precisely tailored for specific applications. We demonstrate that the band gap of the halide perovskite CsPbBr3 can be continuously widened through homovalent substitution of Sr2+ for Pb2+ using solid-state synthesis, creating a material with the formula CsPb1-xSrxBr3 (0 ≤ x ≤ 1). Sr2+ and Pb2+ form a solid solution in CsPb1-xSrxBr3. Pure CsPbBr3 has a band gap of 2.29(2) eV, which increases to 2.64(3) eV for CsPb0.25Sr0.75Br3. The increase in band gap is clearly visible in the color change of the materials and is also confirmed by a shift in the photoluminescence. Density-functional theory calculations support the hypothesis that Sr incorporation widens the band gap without introducing mid-gap defect states. These results demonstrate that homovalent B-site alloying can be a viable method to tune the band gap of simple halide perovskites.

Keywords

perovskite
band gap
doping
halide perovskite
solid solution

Supplementary materials

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Abstract graphic
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The band gap increases as the incorporated amount of Sr increases
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Supporting Information
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Details on photoluminescence lifetime fitting procedure. Figures S1-S7: band gap determination, photoluminescence lifetime, computed projected density of states for all atoms, and band structures.
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