Advances in Colloidal Quantum Dot Superlattice Charge Transport

Colloidal quantum dot (QD) superlattices are an attractive class of materials for next generation electronic devices due to the manifold methods to tune their fundamental properties, including atomic composition, size, shape, and surface functionalization. However, due to their massive surface area to volume ratio and various structural disorder, defects have prevented the realization of a QD superlattice that shows true band-like transport properties. We report on novel superlattice fabrication techniques and characterization techniques, which show a dramatic increase of mobility without the use of electrochemical gating. We use scanning photocurrent microscopy to provide a means of extracting accurate minority carrier diffusion lengths as a function of temperature. We show a significantly improved minority carrier diffusion length and external quantum efficiency compared to amorphous QD lattices. We conclude by discussing our results in the context of rigorous signatures of band-like transport in generic superlattices.