Abstract: Nano-crystalline core and nano-crystalline shell pairings having group I-III-VI material nano-crystalline cores, and methods of fabricating nano-crystalline core and nano-crystalline shell pairings having group I-III-VI material nano-crystalline cores, are described. In an example, a semiconductor structure includes a nano-crystalline core composed of a group I-III-VI semiconductor material. A nano-crystalline shell composed of a second, different, semiconductor material at least partially surrounds the nano-crystalline core. In one specific example, the nano-crystalline core/nano-crystalline shell pairing has a photoluminescence quantum yield (PLQY) of greater than 60%. In another specific example, the nano-crystalline core/nano-crystalline shell pairing is a Type I hetero-structure.