Electrochemical modulation of trap states in PbS QDs and their electrical characterization

The optoelectronic devices based on colloidal lead sulfide quantum dots (PbS QDs) have suffered from electronic trap states in bandgap. The trap state is a source for accelerating carrier recombination and degrading the performance of optoelectronic devices. Here, we treated PbS QD electrochemically using cyclic voltammetry to modulate the density of trap states. The reduction of the trap density in the QD layer after electrochemical treatment was confirmed by the impedance analyzing technique, the thermal admittance spectroscopy. The XPS spectra showed that the QD films are oxidized after the electrochemical treatment, implying that the oxidation of the QD surface regulated the trap density through the electrochemical treatment.