6 research outputs found
Donor–Acceptor–Collector Ternary Crystalline Films for Efficient Solid-State Photon Upconversion
It
is pivotal to achieve efficient triplet–triplet annihilation
based photon upconversion (TTA-UC) in the solid-state for enhancing
potentials of renewable energy production devices. However, the UC
efficiency of solid materials is largely limited by low fluorescence
quantum yields that originate from the aggregation of TTA-UC chromophores
and also by severe back energy transfer from the acceptor singlet
state to the singlet state of the triplet donor in the condensed state.
In this work, to overcome these issues, we introduce a highly fluorescent
singlet energy collector as the third component of donor-doped acceptor
crystalline films, in which dual energy migration, i.e., triplet energy
migration for TTA-UC and succeeding singlet energy migration for transferring
energy to a collector, takes place. To demonstrate this scheme, a
highly fluorescent singlet energy collector was added as the third
component of donor-doped acceptor crystalline films. An anthracene-based
acceptor containing alkyl chains and a carboxylic moiety is mixed
with the triplet donor PtÂ(II) octaethylporphyrin (PtOEP) and the energy
collector 2,5,8,11-tetra-<i>tert</i>-butylperylene (TTBP)
in solution, and simple spin-coating of the mixed solution gives acceptor
films of nanofibrous crystals homogeneously doped with PtOEP and TTBP.
Interestingly, delocalized singlet excitons in acceptor crystals are
found to diffuse effectively over the distance of ∼37 nm. Thanks
to this high diffusivity, only 0.5 mol % of doped TTBP can harvest
most of the singlet excitons, which successfully doubles the solid-state
fluorescent quantum yield of acceptor/TTBP blend films to 76%. Furthermore,
since the donor PtOEP and the collector TTBP are separately isolated
in the nanofibrous acceptor crystals, the singlet back energy transfer
from the collector to the donor is effectively avoided. Such efficient
singlet energy collection and inhibited back energy transfer processes
result in a large increase of UC efficiency up to 9.0%, offering rational
design principles toward ultimately efficient solid-state upconverters
Demographic characteristics of patients according to pre-exposure rabies prophylaxis (N = 322).
Demographic characteristics of patients according to pre-exposure rabies prophylaxis (N = 322).</p
Number of patients with animal exposure according to destination (N = 322).
Number of patients with animal exposure according to destination (N = 322).</p
Characteristics of animal exposure according to animal type (N = 322).
Characteristics of animal exposure according to animal type (N = 322).</p
The Kaplan–Meier curve showing the proportion of exposure-free patients from time of departure according to animal type.
Lines indicate dogs (solid black), cats (dotted red), monkeys (solid blue), and others (dotted green).</p
Countries where exposure occurred according to animal type.
Countries with the highest number of patients exposed to dogs, cats, and monkeys are shown in descending order.</p