Confining Metastable Wurtzite HgTe for Infrared Optoelectronics.

Mercury telluride (HgTe) nanocrystals are cornerstone materials for infrared optoelectronics, yet all previously reported forms of HgTe have crystallized in the zinc blende phase. Here, we develop a comprehensive cation exchange route to access metastable wurtzite (WZ) HgTe in both spherical and nanorod morphologies. Structural and spectroscopic characterizations show that WZ HgTe NCs retain the strong confinement tunability of their optical properties while introducing non-cubic lattice and distinct electronic topology. Ab initio modeling reveals that bulk WZ HgTe is a Dirac semimetal, whereas quantum confinement opens a direct gap that enables bright short-wave infrared emission. High-pressure studies demonstrate an irreversible WZ-to-zinc blende phase transition, consistent with its metastable nature, while the WZ phase remains stable at cryogenic temperatures. Electrically driven light-emitting diodes based on WZ HgTe nanorods exhibit superior electroluminescence beyond 2 μm, establishing a platform bridging topological semimetals and confined infrared emitters.