Abstract
Abstract One-photon up-conversion, also called anti-Stokes photoluminescence (ASPL), is the process whereby photoexcited carriers scavenge thermal energy and are promoted into a higher energy excited state before emitting a photon of greater energy than initially absorbed. Here, we examine how ASPL from CsPbBr3 nanoparticles is modified by coupling with plasmonically active gold nanoparticles deposited on a substrate. Two coupling regimes are examined using confocal fluorescence microscopy: three to four Au nanoparticles per diffraction limited region and monolayer Au nanoparticle coverage of the substrate. In both regimes, CsPbBr3 ASPL is blue-shifted relative to CsPbBr3 deposited on a bare substrate, corresponding to an increase in the thermal energy scavenged per emitted photon. However, with monolayer Au nanoparticle coverage, ASPL is enhanced relative to the conventional Stokes-shifted PL. Together, these phenomena result in a 6.7-fold increase in the amount of thermal energy extracted from the system during optical absorption and reemission.
Highlights
The photoluminescence (PL) produced by semiconductors generally undergoes a Stokes shift, whereby emittedOne of the major hurdles to overcome in order to demonstrate optical cooling is the requirement that a system must have an external quantum efficiency of 99% or higher
CsPbBr3 antiStokes photoluminescence (ASPL) is blueshifted relative to CsPbBr3 deposited on a bare substrate, corresponding to an increase in the thermal energy scavenged per emitted photon
Reabsorption and nonradiative decay lead to thermalization losses that are larger than the amount of thermal energy removed from the system through ASPL
Summary
The photoluminescence (PL) produced by semiconductors generally undergoes a Stokes shift, whereby emitted. When Au nanoparticles are limited to approximately three to four particles for every diffraction-limited region, called low coverage from hereon, the ASPL blue-shifts by as much as 7.2 meV compared with the ASPL of control samples of pure films of CsPbBr3 nanoparticles without Au nanoparticles. When CsPbBr3 nanoparticles are deposited on a substrate coated in a monolayer film of densely packed Au nanoparticles, called uniform coverage from hereon, the ASPL both blue-shifts and increases in intensity relative to the SSPL measured over the same region. The increase in ASPL yield relative to SSPL is due to plasmonic enhancement of the intrinsic ASPL mechanism These two effects, and the accompanying six-fold improvement in overall thermal energy scavenging, may help enable future optoelectronic applications of optical cooling and are an intriguing method of improving the ASPL performance in all-inorganic perovskite nanoparticles by coupling them with Au nanoparticle plasmons
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