Bandlike Transport in PbS Quantum Dot Superlattices with Quantum Confinement.

Optoelectronic devices made from colloidal quantum dots (CQDs) often take advantage of the combination of tunable quantum-confined optical properties and carrier mobilities of strongly coupled systems. In this work, first-principles calculations are applied to investigate the electronic, optical, and transport properties of PbS CQD superlattices. Our results show that even in the regime of strong necking and fusing between PbS CQDs, quantum confinement can be generally preserved. In particular, computed carrier mobilities for simple cubic and two-dimensional square lattices fused along the {100} facets are 2-3 orders of magnitude larger than those of superlattices fused along {110} and {111} facets. The relative magnitude of the electron and hole mobilities strongly depends on the crystal and electronic structures. Our results illustrate the importance of understanding the crystal structure of CQD films and that strongly fused CQD superlattices offer a promising pathway for achieving tunable quantum-confined optical properties while increasing carrier mobilities.