Core/shell structured upconversion nanophosphor and Cd-free quantum dot bilayer?based near infrared photodetectors
- Core/shell structured upconversion nanophosphor and Cd-free quantum dot bilayer?based near infrared photodetectors
- 홍아라; 김정윤; 김수연; 김성일; 이광렬; 장호성
- upconversion; Cd-free quantum dots; luminescent materials; nanophosphors; photodetector
- Issue Date
- Optics letters
- VOL 40, NO 21, 49859-4962
- 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.
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