In this talk, I will present how the structural features of NQDs correlate with their optical properties and the device performances. Specifically, I explain the optical and electrical properties (i.e., single exciton and multi-carrier dynamics) of NQDs in respect to their size and shape. In addition I provide the relationship between the optical and electrical properties of NQDs with the performances of corresponding devices. Furthermore, I introduce recent achievements for high performance light-emitting diodes enabled by the structurally engineered NQDs. At the end, I discuss the state-of-the-art of NQD based optoelectronic applications and their potentials/limitations for practical realization.