Highly transparent phototransistor based on quantum-dots and ZnO bilayers for optical logic gate operation in visible-light

Title
Highly transparent phototransistor based on quantum-dots and ZnO bilayers for optical logic gate operation in visible-light
Authors
한일기정신영김병준조남광박성호전도연강예빈김태영김연상강성준
Keywords
phototransistor; transparent; quantum-dots; ZnO bilayer; optical logic gate; visible light
Issue Date
2020-04
Publisher
RSC advances
Citation
VOL 10, NO 28, 16404
Abstract
Highly transparent optical logic circuits operated with visible light signals are fabricated using phototransistors with a heterostructure comprised of an oxide semiconductor (ZnO) with a wide bandgap and quantum dots (CdSe/ZnS QDs) with a small bandgap. ZnO serves as a highly transparent active channel, while the QDs absorb visible light and generate photoexcited charge carriers. The induced charge carriers can then be injected into the ZnO conduction band from the QD conduction band, which enables current to flow to activate the phototransistor. The photoexcited charge transfer mechanism is investigated using time-resolved photoluminescence spectroscopy, scanning Kelvin probe microscopy, and ultraviolet photoelectron spectroscopy. Measurements show that carriers in the QD conduction band can transfer to the ZnO conduction band under visible light illumination due to a change in the Fermi energy level. Moreover, the barrier for electron injection into the ZnO conduction band from the QD conduction band is low enough to allow photocurrent generation in the QDs/ZnO phototransistor. Highly transparent NOT, NOR, and NAND optical logic circuits are fabricated using the QDs/ZnO heterostructure and transparent indium tin oxide electrodes. This work provides a means of developing highly transparent optical logic circuits that can operate under illumination with low-energy photons such as those found in visible light.
URI
http://pubs.kist.re.kr/handle/201004/71966
ISSN
2046-2069
Appears in Collections:
KIST Publication > Article
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