Electrochemical Charging Effect on the Optical Properties of InP/ZnSe/ZnS Quantum Dots

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2020-10, Vol.16 (41), p.e2003542-n/a
• Main Authors: Park, Jumi, Won, Yu‐Ho, Kim, Taehyung, Jang, Eunjoo, Kim, Dongho
• Format: Article
• Language: English
• Subjects: Augers; Bleaching; Charging; core/multi‐shell; electrochemical charging; Emission analysis; Emitters; Emitters (electron); Indium phosphides; Nanotechnology; Optical properties; Photoluminescence; Quantum dots; Rate constants; Reduction; Shells; spectroelectrochemical properties; Thickness; Zinc selenide; Zinc sulfide
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202003542

Semiconductor quantum dots (QDs) are spotlighted as a key type of emissive material for the next generation of light‐emitting diodes (LEDs). This work presents the investigation of the electrochemical charging effect on the absorption and emission of the InP/ZnSe/ZnS QDs with different mid‐shell thicknesses. The excitonic peak is gradually bleached during electrochemical charging, which is caused by 1Se (or 1Sh) state filling when the electron (or hole) is injected into the InP core. Additional charges also lead to photoluminescence (PL) intensity reduction, however, it is greatly mitigated as the mid‐shell thickness increases. Various PL measurements reveal that the PL reduction under electrochemical charging is attributed to the acoustic phonon‐assisted Auger recombination. Here, the Auger recombination in QDs with a thick mid‐shell is reduced under the electrochemically charged condition, indicating that QDs with larger volume are more stable emitters in charge‐injecting devices such as LEDs. Furthermore, the negative and positive trion Auger recombination rate constants are estimated, respectively, via electrochemical charging. The negative trion Auger rate constants decrease with an increase in the mid‐shell thickness increases, whereas the positive trion Auger rate constants are not heavily reliant on the mid‐shell thickness. The photoluminescence properties of quantum dots (QDs) are vulnerable to electrochemical charging due to Auger recombination between the additional charge and photo‐induced charge carriers. However, the QDs passivated by thicker mid‐shell are relatively stable about the charging owing to small phonon effects and large spatial distribution of charge carriers in the large volume.