Controlling the Electron Coupled State in the Superlattice of PbS Quantum Dots by Replacing Ligands

We report that the emission wavelength of a superlattice of colloidal PbS quantum dots (QDs) was greatly lengthened on replacing their ligands with shorter ones. The long-period close packing was achieved with the aid of a pyramidal hole array prepared on a Si substrate using selective wet etching. The emission energy shift at the ground state was accompanied by an increase in the emission lifetime. These emission properties were attributed to the significant delocalization of the carrier wave function in the QD superlattice having long periodicity.