Cation exchange synthesis of uniform PbSe/PbS core/shell tetra-pods and their use as near-infrared photodetectors

Abstract

In this work we explore the preparation of complex-shaped semiconductor nanostructures composed of different materials via a cationic exchange process in which the cations of the original semiconductor nanostructure are replaced by cations of different metals with preservation of the shape and the anionic framework of the nanocrystals. Utilizing this cation exchange method, we synthesized two new tetrapods for the first time: Cu2-xSe/Cu2-xS and PbSe/PbS, both prepared from CdSe/CdS tetrapods as 'templates'. We also fabricated near-infrared (NIR) photodetectors with a very simple architecture comprising a PbSe/PbS tetrapod layer between two Au electrodes on a glass substrate. When illuminated by a NIR laser, these devices are capable of achieving a responsivity of 11.9 A W(-1) without the use of ligand-exchange processes, thermal annealing or hybrid device architecture. Transient absorption spectroscopy was carried out on these PbSe/PbS tetrapods, the results of which suggest that the branched morphology contributes in part to device performance. Investigation of the charge dynamics of the PbSe/PbS tetrapods revealed an extremely long-lived exciton recombination lifetime of ∼17 ms, which can result in enhanced photoconductive gain. Overall, these heterostructured tetrapods showcase simultaneously the importance of nanoparticle shape, band structure, and surface chemistry in the attainment of NIR photodetection.

Role of the Crystal Structure in Cation Exchange Reactions Involving Colloidal Cu2Se Nanocrystals

“… 6 Reactions involving Cu 2 Se NCs and Pb 2+ ions, in comparison, are much less studied (one notable case is represented by PbSe-PbS heterostructures synthesized from Cu 2 Se–Cu 2 S NHs). 44 − 46 …”

Amine‐Free Synthesis of Colloidal Cesium Lead Halide Perovskite Nanocrystals

“…Because of their strong steric effect, branched capping ligands are usually more preferred for improving the stability of NCs. The phosphine‐based capping ligands, such as trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), and phosphonic acids have been widely used in the synthesis of conventional II–VI semiconductor crystals [42–48] . Because of the highly branched structure and relatively strong coordination ability, the phosphine‐based surface capping groups have been utilized by several research groups to make highly stable PNCs [24,34,39,41,49] …”

Quantum Dots Microstructural Metrology: From Time‐Resolved Spectroscopy to Spatially Resolved Electron Microscopy

“…by Mishra and co-workers using PbSe-seeded PbS tetrapods as an active material. [29] The schematic of tetrapod-based IR photodetector and its temporal response for different excitation light are given in Figure 3d,e. QDs have also been widely applied in biosensing, bioimaging, and drug delivery and the advancement of QD biomedical applications made the possibility of real-time monitoring of the occurrence and development of diseases in living organisms.…”

“…Reproduced with permission. [29] Copyright 2016, The Royal Society of Chemistry. Illustration of ZCIS QDs used as "all-in-one" theranostic nanomedicines with intrinsic fluorescence/MSOT imaging and PTT/PDT therapeutic capabilities.…”

“…They verified that the film is smooth and uniform (Figure 14c). [29] Nevertheless, the accuracy of AFM data heavily depends on the dimension and quality of AFM tips and the sample-tip interaction.…”