Core/shell structured upconversion nanophosphor and Cd-free quantum dot bilayer?based near infrared photodetectors

Title
Core/shell structured upconversion nanophosphor and Cd-free quantum dot bilayer?based near infrared photodetectors
Authors
홍아라김정윤김수연김성일이광렬장호성
Keywords
upconversion; Cd-free quantum dots; luminescent materials; nanophosphors; photodetector
Issue Date
2015-11
Publisher
Optics letters
Citation
VOL 40, NO 21, 49859-4962
Abstract
The core/shell-structured upconversion nanophosphors (UCNPs) and Cd-free CuInS2∕ZnS quantum dots (QDs) were synthesized via coprecipitation and hot-injection methods, respectively, and they were applied to near infrared (NIR) photodetectors. The β-NaYF4:Yb;Er∕β-NaYF4 UCNPs emitted intense visible light peaking at 522, 542, and 656 nm via 2H11∕2, 4S3∕2, and 4F9∕2 → 4I15∕2 transitions under excitation with 980 nm NIR light. The core/ shell UCNPs showed 6.4 times higher emission intensity than core UCNPs. Charge carriers can be generated from CuInS2∕ZnS QDs in the QD-UCNP mixture due to their broad absorption in the visible spectral region shorter than 600 nm. The photodetector devices were fabricated by spincoating CuInS2∕ZnS QDs on a SiO2∕Si substrate with patterned gold electrodes followed by spin-coating UCNPs on the QD layer. The fabricated QD-UCNP-bilayer-based device showed a drastically increased photocurrent (128 μA) compared with the QD-layer-based device under 980 nm NIR light illumination. Additionally, the fabricated device showed stable ON–OFF switching properties against on and off NIR light.
URI
http://pubs.kist.re.kr/handle/201004/50607
ISSN
01469592
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