Issue 29, 2019

Microlens array enhanced upconversion luminescence at low excitation irradiance

Abstract

The dearth of high upconversion luminescence (UCL) intensity at low excitation irradiance hinders the prevalent application of lanthanide-doped upconversion nanoparticles (UCNPs) in many fields ranging from optical bioimaging to photovoltaics. In this work, we propose to use microlens arrays (MLAs) as spatial light modulators to manipulate the distribution of excitation light fields in order to increase UCL, taking advantage of its nonlinear response to the excitation irradiance. We show that multicolored UCL from NaYF4:Yb3+,Er3+@NaYF4:Yb3+,Nd3+ and NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Nd3+ core/shell UCNPs can be increased by more than one order of magnitude under either 980 or 808 nm excitation, by simply placing a polymeric MLA onto the top of these samples. The observed typical green (525/540 nm) and red (654 nm) UCL bands from Er3+ and a blue (450/475 nm) UCL band from Tm3+ exhibit distinct enhancement factors due to their different multi-photon processes. Importantly, our ray tracing simulation reveals that the MLA is able to spatially confine the excitation light (980 and 808 nm) by orders of magnitude, thus amplifying UCL by more than 225-fold (the 450 nm UCL band of Tm3+) at low excitation irradiance. The proposed MLA method has immediate ramifications for the improved performance of all types of UCNP-based devices, such as UCNP-enhanced dye sensitized solar cells demonstrated here.

Graphical abstract: Microlens array enhanced upconversion luminescence at low excitation irradiance

Supplementary files

Article information

Article type
Paper
Submitted
11 apr 2019
Accepted
22 iyn 2019
First published
17 iyl 2019
This article is Open Access
Creative Commons BY-NC license

Nanoscale, 2019,11, 14070-14078

Microlens array enhanced upconversion luminescence at low excitation irradiance

Q. Liu, H. Liu, D. Li, W. Qiao, G. Chen and H. Ågren, Nanoscale, 2019, 11, 14070 DOI: 10.1039/C9NR03105G

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