Beyond Entropy: Leveraging Intrinsic Electronic Character to Induce Internal p-n Domains in Multication Perovskite Semiconductors

Medium-entropy perovskites containing Sn, Zr, Hf, and Te were synthesized via hydrothermal methods. Solid-state NMR confirms a uniform elemental distribution. In these vacancy-ordered double perovskites, the electronic behavior is shaped by more than just entropy. The intrinsic electronic properties of the constituent elements, such as the p-type nature of Sn, Zr, and Hf and the n-type nature of Te, create complex interactions. The simultaneous presence of both carrier types (p- and n-type) leads to emergent behaviors including the formation of spontaneous p-n junctions and localized electric fields. The creation of heterojunctions can lead to complex effects on a material's photoluminescence quantum yield (PLQY). While low concentrations of heterojunctions can boost PLQY, others may introduce new issues that can reduce it. These findings underscore the inadequacy of traditional crystallographic metrics in capturing the complex structure-property relationships that govern the behavior of high-entropy alloys. Effective rational design requires acknowledging that the incorporation of electronically dissimilar B-site cations frequently gives rise to spatially heterogeneous charge transport driven by local domain formation.