We propose and de
monstrate the fabrication of flexible, freestanding fil
ms of InP/ZnS quantu
m dots (QDs) using fatty acid ligands across very large areas (greater than 50 c
m 脳 50 c
m), which have been developed for re
mote phosphor applications in solid-state lighting. E
mbedded in a poly(
methyl
methacrylate)
matrix, although the for
mation of stand鈥揳lone fil
ms using other QDs co
mmonly capped with trioctylphosphine oxide (TOPO) and oleic acid is not efficient, e
mploying
myristic acid as ligand in the synthesis of these QDs, which i
mparts a strongly hydrophobic character to the thin fil
m, enables fil
m for
mation and ease of re
moval even on surprisingly large areas, thereby avoiding the need for ligand exchange. When pu
mped by a blue LED, these Cd-free QD fil
ms allow for high color rendering, war
m white light generation with a color rendering index of 89.30 and a correlated color te
mperature of 2298 K. In the co
mposite fil
m, the te
mperature-dependent e
mission kinetics and energy transfer dyna
mics a
mong different-sized InP/ZnS QDs are investigated and a
model is proposed. High levels of energy transfer efficiency (up to 80%) and strong donor lifeti
me
modification (fro
m 18 to 4 ns) are achieved. The suppression of the nonradiative channels is observed when the hybrid fil
m is cooled to cryogenic te
mperatures. The lifeti
me changes of the donor and acceptor InP/ZnS QDs in the fil
m as a result of the energy transfer are explained well by our theoretical
model based on the exciton鈥揺xciton interactions a
mong the dots and are in excellent agree
ment with the experi
mental results. The understanding of these excitonic interactions is essential to facilitate i
mprove
ments in the fabrication of photo
metrically high quality nanophosphors. The ability to
make such large-area, flexible, freestanding Cd-free QD fil
ms pave the way for environ
mentally friendly phosphor applications including flexible, surface-e
mitting light engines.
Keywords:
miconductor+quantum+dots&qsSearchArea=searchText">Semiconductor quantum dots;
ms&qsSearchArea=searchText">large-area freestanding films;
excitons;
nonradiative energy transfer;
white light generation;
mote+phosphors&qsSearchArea=searchText">remote phosphors