Optimizing the Infrared Photoelectric Detection Performance of Pbs Quantum Dots through Solid-State Ligand Exchange

Abstract

Lead sulfide (PbS) quantum dots (QDs) have attracted a great deal of attention in recent decades, due to their value for applications in optoelectronic devices. However, optimizing the performance of optoelectronic devices through ligand engineering has become a major challenge, as the surfactants that surround quantum dots impede the transport of electrons. In this paper, we prepared PbS QD films and photoconductive devices with four different ligands: 1,2-ethylenedithiol (EDT), tetrabutylammonium iodide (TBAI), hexadecyl trimethyl ammonium bromide (CTAB), and sodium sulfide (Na2S). A series of characterization studies confirmed that using the appropriate ligands in the solid-state ligand exchange step for thin film fabrication can significantly improve the responsivity. The devices treated with sodium sulfide showed the best sensitivity and a wider detection from 400 nm to 2300 nm, compared to the other ligand-treated devices. The responsivity of the champion device reached 95.6 mA/W under laser illumination at 980 nm, with an intensity of 50 mW/cm2.

Two-Step Ligand-Exchange-Assisted Charge Transfer in Graphene/PbS Quantum Dots Hybrid Near-Infrared Photodetector

“…The TBAI enables the I – ions to further replace the long-chain ligand (OA – ) and then the EDT is employed to passivate the surface defects of the quantum dots. In contrast to our earlier results, we achieved excellent device performance based on the two-step treatment of the hybrid photodetector . It is shown that the improved passivation together with slower voltage decay indicates fewer surface trap states and less carrier recombination.…”

“…This is attributed to the increased capacity for charge carrier transport, a narrower gap between QDs, and a reduction in surface defects on QDs, which contribute to higher binding energy. 29 On the other hand, the EDT has a good surface passivation effect, thus reducing the defect density on the surface of the QDs induced by exposed hanging bonds (Figure S5). 39 QDs continued to be treated with the EDT(MAI/TBAI/EDT QDs), MAI/TBAI/EDT QDs have significant electrical properties.…”

“…It is attributed to the defects generated on the surface after treatment with the MAI, which hinder the transport of charge carriers and lead to the reduction of dark current. , Nonetheless, the substitution of ligands with EDT leads to an escalation in the dark current of the device. This is attributed to the increased capacity for charge carrier transport, a narrower gap between QDs, and a reduction in surface defects on QDs, which contribute to higher binding energy . On the other hand, the EDT has a good surface passivation effect, thus reducing the defect density on the surface of the QDs induced by exposed hanging bonds (Figure S5).…”

“…In contrast to our earlier results, we achieved excellent device performance based on the two-step treatment of the hybrid photodetector. 29 It is shown that the improved passivation together with slower voltage decay indicates fewer surface trap states and less carrier recombination. This opens up a wide range of possibilities for creating high-responsivity and focus plane array infrared detectors suitable for applications in imaging, communications, and sensing.…”

Design and optimization of the performance of PbS quantum dot based vertical photodetector

“…The optical properties required for SCAPS software calculations are the optical absorption coefficients, which are obtained from the SCAPS absorption file database for ZnO shown in figure 2. (d), and from synthesis and testing in our laboratory [29,30] for PbS quantum dots. The quantum dots synthesized by the sol-gel method at 150  C were dissolved in toluene to form a 0.3 mg ml −1 solution, and the absorbance of solution A( ) l was tested under an ultraviolet (UV) spectrophotometer to obtain the absorption coefficient ( ) a l of the quantum dots, which was then normalized such that ( ) a l at the first exciton absorption peak was equal to the absorption coefficient value for bulk PbS film at this wavelength [31,32].…”