Superlattice Fabrication for Designer Mesoscale Quantum Dot Solids
Colloidal quantum dot (QD) solids have long been considered a promising nanomaterial, combining the wide range of material property-tuning capabilities associated with the nanoscale and the potential for comparable performance in optoelectronic and photovoltaic applications to those of a conventional bulk material. However, most research in this field focuses on amorphous QD solids, the extremely short-range order of which greatly hinders charge transport within the film. To counter this, we have developed a fabrication method for three-dimensional PbSe QD superlattices that utilizes self-assembly on a liquid subphase, as well as photo-triggered formation of the desired epitaxially-fused superlattice (epi-SL). These epi-SLs possess high spatial order, with crystalline grains on the micron length scale, and carrier mobilities several orders of magnitude higher than that of an amorphous QD film. Combining this with atomic layer deposition infilling will passivate any remaining defect states within the epi-SL, eventually triggering mini-band formation and achieving delocalized charge transport similar to that observed in bulk semiconductors.