On the limits of Zn doping in dual-polyhedral Cs₇Cd₃Br₁₃

Low-dimensional metal halides featuring self-trapped exciton emission have emerged as self-absorption-free emitters for applications in solid-state lighting, scintillators, and luminescent solar concentrators. One recent addition to this materials family is Cs₇Cd₃Br₁₃, which exhibits a complex mixed 1D-0D structure with isolated [CdBr₄]²⁻ tetrahedra and corner-connected 1D chains of [CdBr₄Br_2/2]³⁻ octahedra. Here, we develop a strategy to dope Zn²⁺ (an isoelectronic dopant that will selectively substitute the tetrahedral site) into Cs₇Cd₃Br₁₃ to learn more about what drives emission in this dual-polyhedral system. We test the range of substitution from 0 to 67% (where 2/3 substitution would displace 100% of the tetrahedral Cd atoms), finding that the upper limit is significantly lower than expected at 7.5% Zn. This low limit arises from non-luminescent competing phases Cs₃CdBr₅ and Cs₂ZnBr₄. This work highlights the complexity of this compound and will enable further study of the details of self-trapped exciton emission in Zn-doped Cs₇Cd₃Br₁₃.