Enhanced film quality of PbS QD solid by eliminating the oxide traps through an in situ surface etching and passivation

Abstract

PbS QDs have attracted considerable interest in optoelectronics. However, their high susceptibility to oxidation results in the production of Pb oxides on PbS, which can induce sub-bandgap traps in PbS QDs that are detrimental to the performance of the resultant device. Here we report a facile strategy to enhance the film quality of PbS QD solids through an in situ surface etching and passivation route, carried out by immersing the PbS QD solid film in an I⁻/I₂ solution at room temperature in ambient air. The process is simple and allows for the simultaneous removal of surface Pb oxides and the formation of a PbI₂ passivation layer on PbS QDs, leading to the elimination of traps in PbS QDs while preserving their optical properties and film morphology. As a result, charge recombination within the film is suppressed and charge carrier transport is enhanced. When used to fabricate a quantum dot sensitized solar cell, a large increase in cell performance was achieved.