Thiol and Halometallate, Mutually Passivated Quantum Dot Ink for Photovoltaic Application

Tunable band gap colloidal QDs is a potential building block to harvest the wide energy solar spectrum. The solution-phase surface passivation with lead halide based halometallate ligands has remarkably simplified the processing of quantum dots (QDs) and enabled the proficient use of materials for the development of solar cells. It is; however, shown that the hallometalate ligand passivated QD ink, allow the formation of thick crystalline shell layer which limits the carrier transport of the QD solids. Organic thiols have long been used to develop QD solar cell using solid-state ligand exchange approach. However, their use is limited in solution-phase passivation due to poor dispersity of thiol treated QDs in common solvents. In this report, a joint passivation strategy using thiol and halometallate ligand is developed to prepare the QD ink. The mutually passivated QDs show a 50% reduction in shell thickness, reduced trap density and improved monodispersity in their solid films. These improvements lead to...