2 research outputs found
Excited State Intramolecular Proton Transfer Dynamics of 1‑Hydroxy-2-acetonaphthone
Excited
state intramolecular proton transfer (ESIPT) of 1-hydroxy-2-acetonaphthone
(HAN) has been in controversy, mainly because its Stokes shift is
small compared to those of typical ESIPT molecules. We have investigated
excited state dynamics of HAN by time-resolved fluorescence with a
resolution high enough to record the nuclear wave packet motions in
the excited state. Population dynamics of both the normal and tautomer
forms were recorded together with the wave packet motions of the tautomer
in the excited state, which confirm the ESIPT of HAN. The population
dynamics of the normal and tautomer forms imply that the ESIPT dynamics
is biphasic with two time constants <25 and 80 fs. Theoretical
analysis of the vibrational modes of the tautomer excited impulsively
reveals that major part of the change for the ESIPT reaction is on
the naphthalene ring
Effects of Gold-Nanoparticle Surface and Vertical Coverage by Conducting Polymer between Indium Tin Oxide and the Hole Transport Layer on Organic Light-Emitting Diodes
The effect of varying
degrees of surface and vertical coverage
of gold nanoparticles (Au-NPs) by polyÂ(styrenesulfonate)-doped polyÂ(3,4-ethylenedioxythiophene)
(PEDOT:PSS), which was used as a capping layer between indium tin
oxide (ITO) and a hole transport layer (HTL) on small-molecule fluorescent
organic light-emitting diodes (OLEDs), was systemically investigated.
With respect to the Au-NP loading amount and size, the resultant current
densities influenced the charge balance and, therefore, the OLED device
performance. When the capping layer consisted of ITO/Au-NPs/PEDOT:PSS+Au-NPs,
superior device performance was obtained with 10-nm Au-NPs through
increased surface coverage in comparison to other Au-NP PEDOT:PSS
coverage conditions. Furthermore, the Au-NP size determined the vertical
coverage of the capping layer. The current densities of OLEDs containing
small Au-NPs (less than 30 nm, small vertical coverage) covered by
PEDOT:PSS decreased because of the suppression of the hole carriers
by the Au-NP trapping sites. However, the current densities of the
devices with large Au-NPs (over 30 nm, large vertical coverage) increased.
The increased electromagnetic fields observed around relatively large
Au-NPs under electrical bias were attributed to increased current
densities in the OLEDs, as confirmed by the finite-difference time-domain
simulation. These results show that the coverage conditions of the
Au-NPs by the PEDOT:PSS clearly influenced the OLED current density
and efficiency