Permanent Electrochemical Doping of Quantum Dot Films through Photopolymerization of Electrolyte Ions

Abstract

Quantum dots (QDs) are considered for devices like light-emitting diodes (LEDs) and photodetectors as a result of their tunable optoelectronic properties. To utilize the full potential of QDs for optoelectronic applications, control over the charge carrier density is vital. However, controlled electronic doping of these materials has remained a long-standing challenge, thus slowing their integration into optoelectronic devices. Electrochemical doping offers a way to precisely and controllably tune the charge carrier concentration as a function of applied potential and thus the doping levels in QDs. However, the injected charges are typically not stable after disconnecting the external voltage source because of electrochemical side reactions with impurities or with the surfaces of the QDs. Here, we use photopolymerization to covalently bind polymerizable electrolyte ions to polymerizable solvent molecules after electrochemical charge injection. We discuss the importance of using polymerizable dopant ions as compared to nonpolymerizable conventional electrolyte ions such as LiClO 4 when used in electrochemical doping. The results show that the stability of charge carriers in QD films can be enhanced by many orders of magnitude, from minutes to several weeks, after photochemical ion fixation. We anticipate that this novel way of stable doping of QDs will pave the way for new opportunities and potential uses in future QD electronic devices.

Electrochemical Control of Strong Coupling of CdSe Exciton-Polaritons in Plasmonic Cavities

“…63,64 Ultimately, we attribute the incomplete removal of electrons and restoration of strong coupling during the cycling experiment to limitations on the rate or amount of charge that can be added or removed. 56,65 In conclusion, we demonstrate that the coupling between CdSe NPLs and a plasmonic lattice cavity can be actively tuned across the strong and weak coupling regimes. The magnitude of the coupling lost and recovered correlates to the number of charges injected or removed from the NPL film.…”

“…The incomplete reduction of the film in the first cycle can be explained by the localization of electrochemically injected charge. − As electrons are injected into the NPL film, cations from the electrolyte ([Bu 4 N] + ) are also drawn into the film voids. , The reduction of NPLs is restricted by the uptake of charge-compensating ions that depend on the size of the counterion, the void space of the NPL film, and the length of the NPL ligands . Therefore, experimental differences in NPL film thickness or packing density can propagate to differences in the NPL reduction efficiency.…”

“…Injected charge can also be trapped in localized states at the NPL surface that will affect conduction band population and limit the full reduction of the NPL film in each cycle within experiment time scales. ,,,− Charge trapping at NPL surface states may also result in chemically irreversible degradation . The complications of electrochemically injected charge affect not only the addition of electrons but also the efficient removal of all added electrons in the discharge step. , Additionally, injected charges can react with solvent impurities and prevent injected electrons from reducing the film. , Ultimately, we attribute the incomplete removal of electrons and restoration of strong coupling during the cycling experiment to limitations on the rate or amount of charge that can be added or removed. , …”

Facile Photopolymerization of High-Molecular-Weight Polyaniline Composites Induced by g-C3N4 at Room Temperature for Trace Fe Ion Sensors

“…Photopolymerization technology has rarely been studied in the synthesis of conductive polymers . Compared with traditional thermal polymerization, photopolymerization has the advantages of a harmonious environment, high production efficiency, and low energy consumption . Sury et al synthesized conductive PANI by photopolymerization with the aniline (ANI) monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linking agent, and dimethoxy phenylacetophenone as the initiator .…”